Semiconductor device manufacturing method and wafer-attached structure

ABSTRACT

A method for manufacturing a semiconductor device includes a step of preparing a semiconductor wafer source which includes a first main surface on one side, a second main surface on the other side and a side wall connecting the first main surface and the second main surface, an element forming step of setting a plurality of element forming regions on the first main surface of the semiconductor wafer source, and forming a semiconductor element at each of the plurality of element forming regions, and a wafer source separating step of cutting the semiconductor wafer source from a thickness direction intermediate portion along a horizontal direction parallel to the first main surface, and separating the semiconductor wafer source into an element formation wafer and an element non-formation wafer after the element forming step.

TECHNICAL FIELD

The present invention relates to a method for manufacturing asemiconductor device, and a wafer-attached structure.

BACKGROUND ART

Patent Literature 1 discloses a method for manufacturing a semiconductordevice which includes a step of grinding and thinning a semiconductorwafer and a step of cutting out a plurality of semiconductor chips(semiconductor devices) from the thinned semiconductor wafer.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Publication No.2010-016188.

SUMMARY OF INVENTION Technical Problem

In recent years, with the development of semiconductor devicemanufacturing technology, semiconductor devices have been made thinner.On the other hand, with the development of semiconductor devicemanufacturing technology, semiconductor wafers have been made larger indiameter. A semiconductor wafer is increased in thickness in proportionto a size of diameter from the viewpoint of suppressing deflection,etc., due to its own weight. That is, the semiconductor wafermanufacturing technology is proceeding in a direction of increasing thethickness of the semiconductor wafer, contrary to the manufacturingtechnology of the semiconductor device intended to reduce the thicknessof the semiconductor device.

For example, in a conventional manufacturing method disclosed in PatentLiterature 1, a plurality of semiconductor devices are cut out after athick semiconductor wafer is ground and thinned. This manufacturingmethod is able to manufacture a semiconductor device with a desiredthickness, regardless of the thickness of a semiconductor wafer.

However, in the case of the conventional manufacturing method, when asemiconductor wafer is increased in thickness, the portion of thesemiconductor wafer to be removed by grinding increases. That is,according to the conventional manufacturing method, a semiconductorwafer larger in diameter and thicker in thickness results in a longertime of grinding for thinning a semiconductor device and also a relativedecrease in the number of obtained semiconductor devices per unitvolume, as compared with a semiconductor wafer smaller in diameter andthinner in thickness. For this reason, the semiconductor wafer cannot beconsumed efficiently.

A preferred embodiment of the present invention provides a method formanufacturing a semiconductor device capable of efficiently consuming asemiconductor wafer, and a wafer-attached structure capable of the same.

Solution to Problem

A preferred embodiment of the present invention provides a method formanufacturing a semiconductor device including a step of preparing asemiconductor wafer source which includes a first main surface on oneside, a second main surface on the other side and a side wall connectingthe first main surface and the second main surface, an element formingstep of setting a plurality of element forming regions on the first mainsurface of the semiconductor wafer source, and forming a semiconductorelement at each of the plurality of element forming regions, and a wafersource separating step of cutting the semiconductor wafer source from athickness direction intermediate portion along a horizontal directionparallel to the first main surface, and separating the semiconductorwafer source into an element formation wafer (element formed wafer) andan element non-formation wafer after the element forming step.

According to this method for manufacturing the semiconductor device,while a plurality of semiconductor devices can be cut out from theelement formation wafer (element formed wafer), the elementnon-formation wafer can also be reused as a new semiconductor wafersource. Thereby, it is possible to suppress a manufacturing delay andalso suppress an excessive consumption of the semiconductor wafersource. Thus, it is possible to provide the method for manufacturing thesemiconductor device capable of efficiently consuming the semiconductorwafer source.

A preferred embodiment of the present invention provides awafer-attached structure including a semiconductor wafer source having afirst main surface as an element forming surface and a second mainsurface positioned on the opposite side of the first main surface, andhaving a thickness enough to be cut along a horizontal directionparallel to the first main surface from a thickness directionintermediate portion, and a supporting member having a first supportingmain surface attached to the second main surface of the semiconductorwafer source and a second supporting main surface positioned on theopposite side of the first supporting main surface.

According to this wafer-attached structure, the semiconductor wafersource having a semiconductor element in the first main surface can becut along a horizontal direction parallel to the first main surface froma thickness direction intermediate portion thereof. Thereby, it ispossible to separate the semiconductor wafer source into an elementformation wafer (element formed wafer) having a semiconductor elementand an element non-formation wafer.

Then, while a plurality of semiconductor devices can be cut out from theelement formation wafer, the element non-formation wafer supported onthe supporting member can also be reused as a new semiconductor wafersource. Thereby, it is possible to suppress a manufacturing delay andalso suppress an excessive consumption of the semiconductor wafersource. Thus, it is possible to provide a wafer-attached structurecapable of efficiently consuming the semiconductor wafer source.

The aforementioned or other objects, features, and effects of thepresent invention will be clarified by the following description ofpreferred embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a perspective view for describing one example of asemiconductor wafer source which is applicable to a method formanufacturing a semiconductor device according to a first preferredembodiment of the present invention.

FIG. 1B is a perspective view for describing one example of awafer-attached structure which is applicable to the method formanufacturing the semiconductor device according to the first preferredembodiment of the present invention.

FIG. 2A is a process chart for describing the method for manufacturingthe semiconductor device according to the first preferred embodiment ofthe present invention.

FIG. 2B is a process chart for describing a step performed on an elementformation wafer obtained from a step shown in FIG. 2A.

FIG. 3A is a schematic cross sectional view for describing themanufacturing method shown in FIG. 2A and FIG. 2B.

FIG. 3B is a cross sectional view for describing a step subsequent tothat of FIG. 3A.

FIG. 3C is a cross sectional view for describing a step subsequent tothat of FIG. 3B.

FIG. 3D is a cross sectional view for describing a step subsequent tothat of FIG. 3C.

FIG. 3E is a cross sectional view for describing a step subsequent tothat of FIG. 3D.

FIG. 3F is a cross sectional view for describing a step subsequent tothat of FIG. 3E.

FIG. 3G is a cross sectional view for describing a step subsequent tothat of FIG. 3F.

FIG. 3H is a cross sectional view for describing a step subsequent tothat of FIG. 3G.

FIG. 3I is a cross sectional view for describing a step subsequent tothat of FIG. 3H.

FIG. 3J is a cross sectional view for describing a step subsequent tothat of FIG. 3I.

FIG. 3K is a cross sectional view for describing a step subsequent tothat of FIG. 3J.

FIG. 4 is a process chart for describing a method for manufacturing asemiconductor device according to a second preferred embodiment of thepresent invention.

FIG. 5 is a process chart for describing a method for manufacturing asemiconductor device according to a third preferred embodiment of thepresent invention.

FIG. 6A is a process chart for describing a method for manufacturing asemiconductor device according to a fourth preferred embodiment of thepresent invention.

FIG. 6B is a process chart for describing a step performed on an elementformation wafer obtained from the step shown in FIG. 6A.

FIG. 7A is a schematic cross sectional view for describing themanufacturing method shown in FIG. 6A and FIG. 6B.

FIG. 7B is a cross sectional view for describing a step subsequent tothat of FIG. 7A.

FIG. 7C is a cross sectional view for describing a step subsequent tothat of FIG. 7B.

FIG. 7D is a cross sectional view for describing a step subsequent tothat of FIG. 7C.

FIG. 7E is a cross sectional view for describing a step subsequent tothat of FIG. 7D.

FIG. 7F is a cross sectional view for describing a step subsequent tothat of FIG. 7E.

FIG. 7G is a cross sectional view for describing a step subsequent tothat of FIG. 7F.

FIG. 8A is a process chart for describing a method for manufacturing asemiconductor device according to a fifth preferred embodiment of thepresent invention.

FIG. 8B is a process chart for describing a step performed on an elementformation wafer obtained from the step shown in FIG. 8A.

FIG. 9A is a schematic cross sectional view for describing themanufacturing method shown in FIG. 8A and FIG. 8B.

FIG. 9B is a cross sectional view for describing a step subsequent tothat of FIG. 9A.

FIG. 9C is a cross sectional view for describing a step subsequent tothat of FIG. 9B.

FIG. 9D is a cross sectional view for describing a step subsequent tothat of FIG. 9C.

FIG. 9E is a cross sectional view for describing a step subsequent tothat of FIG. 9D.

FIG. 9F is a cross sectional view for describing a step subsequent tothat of FIG. 9E.

FIG. 9G is a cross sectional view for describing a step subsequent tothat of FIG. 9F.

FIG. 9H is a cross sectional view for describing a step subsequent tothat of FIG. 9G.

FIG. 9I is a cross sectional view for describing a step subsequent tothat of FIG. 9H.

FIG. 9J is a cross sectional view for describing a step subsequent tothat of FIG. 9I.

FIG. 9K is a cross sectional view for describing a step subsequent tothat of FIG. 9J.

FIG. 9L is a cross sectional view for describing a step subsequent tothat of FIG. 9K.

FIG. 9M is a cross sectional view for describing a step subsequent tothat of FIG. 9L.

FIG. 10 is a cross sectional view of showing a semiconductor deviceaccording to one example of the present invention.

FIG. 11A is a process chart for describing a method for manufacturing asemiconductor device according to a sixth preferred embodiment of thepresent invention.

FIG. 11B is a process chart for describing a step performed on anelement formation wafer obtained from the step shown in FIG. 11A.

FIG. 12A is a schematic cross sectional view for describing themanufacturing method shown in FIG. 11A and FIG. 11B by applying themanufacturing method shown in FIG. 11A and FIG. 11B to the method formanufacturing the semiconductor device shown in FIG. 10.

FIG. 12B is a cross sectional view for describing a step subsequent tothat of FIG. 12A.

FIG. 12C is a cross sectional view for describing a step subsequent tothat of FIG. 12B.

FIG. 12D is a cross sectional view for describing a step subsequent tothat of FIG. 12C.

FIG. 12E is a cross sectional view for describing a step subsequent tothat of FIG. 12D.

FIG. 12F is a cross sectional view for describing a step subsequent tothat of FIG. 12E.

FIG. 12G is a cross sectional view for describing a step subsequent tothat of FIG. 12F.

FIG. 12H is a cross sectional view for describing a step subsequent tothat of FIG. 12G.

FIG. 12I is a cross sectional view for describing a step subsequent tothat of FIG. 12H.

FIG. 13 is a cross sectional view of showing a first modificationexample of a wafer-attached structure.

FIG. 14 is a perspective view of showing a second modification exampleof the wafer-attached structure.

DESCRIPTION OF EMBODIMENTS

FIG. 1A is a perspective view for describing one example of asemiconductor wafer source 1 which is applicable to the method formanufacturing the semiconductor device according to the first preferredembodiment of the present invention.

With reference to FIG. 1A, a disc-shaped semiconductor wafer source 1may be applied to the manufacture of a semiconductor device. In thismode, the semiconductor wafer source 1 includes SiC (silicon carbide).More specifically, the semiconductor wafer source 1 is made of an SiCmonocrystal semiconductor wafer.

The semiconductor wafer source 1 has a first main surface 2 on one side,a second main surface 3 on the other side, and a side wall 4 connectingthe first main surface 2 and the second main surface 3. The first mainsurface 2 of the semiconductor wafer source 1 is an element formingsurface in which a semiconductor element is formed.

The semiconductor wafer source 1 has a thickness T1 allowing of beingcut along a horizontal direction parallel to the first main surface 2from a thickness direction intermediate portion thereof. The thicknessT1 of the semiconductor wafer source 1 exceeds the thickness of asemiconductor substrate of a semiconductor device (semiconductor chip)which is to be obtained. The thickness T1 of the semiconductor wafersource 1 may be not less than 100 μm and not more than 1000 μm. Thethickness T1 of the semiconductor wafer source 1 may be not less than250 μm and not more than 500 μm.

The semiconductor wafer source 1 includes a first wafer edge portion 5and a second wafer edge portion 6. The first wafer edge portion 5connects the first main surface 2 and the side wall 4. Morespecifically, the first wafer edge portion 5 connects the first mainsurface 2 and the side wall 4 at a right angle. That is, the first waferedge portion 5 is not chamfered.

The second wafer edge portion 6 connects the second main surface 3 andthe side wall 4. More specifically, the second wafer edge portion 6connects the second main surface 3 and the side wall 4 at a right angle.That is, the second wafer edge portion 6 is not chamfered. In thesemiconductor wafer source 1, it is preferable that at least the secondwafer edge portion 6 is not chamfered.

A first orientation flat 7 (first mark) which indicates a crystalorientation, etc., is formed in the semiconductor wafer source 1. Thefirst orientation flat 7 includes a notched portion formed at aperipheral edge of the semiconductor wafer source 1. The firstorientation flat 7 extends linearly at a peripheral edge of thesemiconductor wafer source 1.

A plurality of element forming regions 10 (chip forming regions) are setin the first main surface 2 of the semiconductor wafer source 1. Asemiconductor element 11 is formed in each of the plurality of elementforming regions 10. The plurality of element forming region 10 may beset in a matrix form at a mutually spaced interval from each other. Eachof the element forming regions 10 may be set in a rectangular shape in aplan view as viewed from a normal direction of the first main surface 2.

The semiconductor element 11 may include various functional elementsformed by using a semiconductor material, properties of semiconductormaterials, or the like. The semiconductor element 11 may include atleast any one of a semiconductor rectifier element, a semiconductorswitching element and a semiconductor passive element.

The semiconductor rectifier element may include various types of diodeelements such as a pn junction diode, a Zener diode, a Schottky barrierdiode and a fast recovery diode. The semiconductor switching element mayinclude various types of transistors such as a bipolar transistor, aMISFET (Metal Insulator Semiconductor Field Effect Transistor), and anIGBT (Insulated Gate Bipolar Transistor). The semiconductor passiveelement may include various types of passive elements such as acapacitor, a resistor and an inductor.

The semiconductor element 11 may include a circuit network in which anytwo or more of a semiconductor rectifier element, a semiconductorswitching element and a semiconductor passive element are selectivelycombined. The circuit network may form a part of or an entirety of anintegrated circuit.

The integrated circuit may include an SSI (Small Scale Integration), anLSI (Large Scale Integration), an MSI (Medium Scale Integration), a VLSI(Very Large Scale Integration) and a ULSI (Ultra-Very Large ScaleIntegration).

A dicing line 12 is defined at a boundary region between the pluralityof element forming regions 10. The semiconductor wafer source 1 is cutalong the dicing line 12, so that a plurality of semiconductor devicesare cut out.

FIG. 1B is a perspective view for describing one example of awafer-attached structure 101 which is applicable to the method formanufacturing the semiconductor device according to the first preferredembodiment of the present invention.

With reference to FIG. 1B, a disc-shaped wafer-attached structure 101may be applied to the manufacture of the semiconductor device. Thewafer-attached structure 101 has a laminated structure which includes asemiconductor wafer source 1 and a first supporting member 21. Thesemiconductor wafer source 1 is attached to the first supporting member21.

According to the wafer-attached structure 101, the semiconductor wafersource 1 and the first supporting member 21 are handled in an integratedmanner. Thereby, the convenience in handling the semiconductor wafersource 1 is enhanced. In this description, term “handling” includes notonly carrying in/carrying out of an apparatus for manufacturingsemiconductor devices but also the distribution thereof to market. Thatis, the wafer-attached structure 101 can be a transaction object in amarket.

The first supporting member 21 is made of a disc-shaped substrate(wafer) and supports the semiconductor wafer source 1 from the secondmain surface 3 side. The first supporting member 21 has a firstsupporting main surface 22 on one side, a second supporting main surface23 on the other side and a supporting side wall 24 connecting the firstsupporting main surface 22 and the second supporting main surface 23.

The first supporting member 21 includes a first supporting edge portion25 and a second supporting edge portion 26. The first supporting edgeportion 25 connects the first supporting main surface 22 and thesupporting side wall 24. The first supporting edge portion 25 includes achamfered portion which is chamfered. The first supporting edge portion25 may be C-chamfered. The first supporting edge portion 25 may beR-chamfered. In this case, the first supporting edge portion 25 mayinclude a chamfered portion which is chamfered in a convexly curvedshape or a shape close to a convexly curved shape.

The first supporting edge portion 25 may be chamfered at least by anyone of a wire saw processing method, a dicing blade processing methodand an etching processing method. The handling convenience of thewafer-attached structure 101 is increased by chamfering of the firstsupporting edge portion 25.

The second supporting edge portion 26 connects the second supportingmain surface 23 and the supporting side wall 24. The second supportingedge portion 26 includes a chamfered portion which has been chamfered.The second supporting edge portion 26 may be C-chamfered. The secondsupporting edge portion 26 may be R-chamfered. In this case, the secondsupporting edge portion 26 may include a chamfered portion which ischamfered in a convexly curved shape or in a shape close to a convexlycurved shape.

The second supporting edge portion 26 may be chamfered at least by anyone of a wire saw processing method, a dicing blade processing methodand an etching processing method. The handling convenience of thewafer-attached structure 101 is increased by chamfering of the secondsupporting edge portion 26.

The first supporting member 21 supports the semiconductor wafer source 1from the second main surface 3 side. That is, the semiconductor wafersource 1 is arranged on the first supporting main surface 22 of thefirst supporting member 21 in a posture in which the second main surface3 faces the first supporting main surface 22 of the first supportingmember 21. The first supporting main surface 22 of the first supportingmember 21 is attached to the second main surface 3 of the semiconductorwafer source 1.

In this mode, the first supporting member 21 is formed such as to belarger in planar area than the semiconductor wafer source 1. Thewafer-attached structure 101 can be handled more conveniently. In astate in which the semiconductor wafer source 1 is supported at thecentral portion of the first supporting member 21, a distance D betweena peripheral edge of the semiconductor wafer source 1 and a peripheraledge of the first supporting member 21 may be not less than 0 mm and notmore than 10 mm.

Various types of materials can be used as a material of the firstsupporting member 21 as long as they are able to fix and support thesemiconductor wafer source 1. In view of supporting the semiconductorwafer source 1, it is preferable that the first supporting member 21 hasphysical properties relatively close to those of the semiconductor wafersource 1. The physical properties include, for example, a thermalexpansion coefficient and a melting point.

A ratio of thermal expansion coefficient of the first supporting member21 in relation to the thermal expansion coefficient of the semiconductorwafer source 1 may be not less than 0.5 and not more than 1.5. It ispreferable that the thermal expansion coefficient ratio is not less than0.8 and not more than 1.2. A melting point of the first supportingmember 21 may be not less than a melting point of the semiconductorwafer source 1. The melting point of the first supporting member 21 maybe not less than 1600° C.

It is preferable that the first supporting member 21 includes a materialthat is the same type as the semiconductor wafer source 1. That is, thefirst supporting member 21 preferably includes SiC (silicon carbide). Itis more preferable that the first supporting member 21 is made of an SiCmonocrystal semiconductor wafer. Thereby, physical properties of thefirst supporting member 21 are approximately equal to those of thesemiconductor wafer source 1.

A thickness T2 of the first supporting member 21 may be not less than100 μm and not more than 1000 μm. The thickness T2 of the firstsupporting member 21 may be not less than 250 μm and not more than 500μm. The thickness T2 of the first supporting member 21 may be equal tothe thickness T1 of the semiconductor wafer source 1.

In the method for manufacturing the semiconductor device, laser lightmay be irradiated onto the semiconductor wafer source 1 via the firstsupporting member 21. In this case, it is preferable that the firstsupporting member 21 is optically transparent. The first supportingmember 21 is preferably a light permeable wafer which suppressesattenuation of laser light irradiated into the semiconductor wafersource 1. The light permeable wafer may include a translucent wafer anda transparent wafer.

The first supporting member 21 is preferably a monocrystal semiconductorwafer (SiC monocrystal semiconductor wafer) with which no impurities aredoped or which is low in concentrations of impurities. In this case,absorption (attenuation) of laser light by the first supporting member21 is suppressed.

In a case in which the first supporting member 21 includes impurities,the first supporting member 21 is preferably not more than 1.0×10¹⁸ cm⁻³in concentrations of impurities. It should be noted that laser lighthaving a wavelength of not more than 390 μm has a tendency of beingabsorbed (attenuated) by the first supporting member 21 made of an SiCmonocrystal semiconductor wafer, regardless of whether impurities aredoped.

The first supporting member 21 may be a monocrystal semiconductor wafer(SiC monocrystal semiconductor wafer) with which vanadium is doped. Thefirst supporting member 21 may be a monocrystal semiconductor wafer (SiCmonocrystal semiconductor wafer) with which p type impurities are doped.The first supporting member 21 may be a monocrystal semiconductor wafer(SiC monocrystal semiconductor wafer) with which n type impurities aredoped.

The first supporting member 21 may be a monocrystal semiconductor wafer(SiC monocrystal semiconductor wafer) with which p type impurities and ntype impurities are doped. The p type impurities and the n typeimpurities may be similar in concentrations. In other modes, the firstsupporting member 21 made of various types of materials can be adoptedon the basis of physical properties of the semiconductor wafer source 1and a wavelength of laser light.

A second orientation flat 27 (second mark) which indicates a crystalorientation, etc., is formed in the first supporting member 21. Thesecond orientation flat 27 includes a notched portion which is formed ata peripheral edge of the first supporting member 21. The secondorientation flat 27 extends linearly at a peripheral edge of the firstsupporting member 21.

The second orientation flat 27 of the first supporting member 21 mayindicate a crystal orientation equal to that of the first orientationflat 7 of the semiconductor wafer source 1. Thereby, it is possible toattach the semiconductor wafer source 1 to the first supporting member21, with the crystal orientation understood.

The second orientation flat 27 of the first supporting member 21 may bepositionally aligned with the first orientation flat 7 of thesemiconductor wafer source 1. That is, the second orientation flat 27may extend in parallel along the first orientation flat 7 at a positionproximate to the first orientation flat 7.

Thereby, the crystal orientation of the semiconductor wafer source 1 isin agreement with that of the first supporting member 21, thus making itpossible to easily judge the crystal orientation of the semiconductorwafer source 1. Thereby, it is possible to increase the handlingconvenience of the wafer-attached structure 101.

FIG. 2A is a process chart for describing the method for manufacturingthe semiconductor device according to the first preferred embodiment ofthe present invention. FIG. 2B is a process chart for describing a stepperformed on an element formation wafer 41 (new semiconductor wafersource 51, element formed wafer) obtained from the step shown in FIG.2A.

FIG. 3A to FIG. 3K are each a schematic cross sectional view fordescribing the manufacturing method shown in FIG. 2A and FIG. 2B. InFIG. 3A to FIG. 3K, for the sake of convenience of description, astructure of the semiconductor wafer source 1 and that of the firstsupporting member 21 are shown in a simplified manner.

First, with reference to FIG. 3A, the semiconductor wafer source 1 isprepared (Step S1 of FIG. 2A). The first supporting member 21 is alsoprepared.

Next, with reference to FIG. 3B, the semiconductor wafer source 1 isattached to the first supporting member 21 (Step S2 of FIG. 2A). Thesemiconductor wafer source 1 is attached to the first supporting member21 in a posture that the second main surface 3 faces the firstsupporting main surface 22 of the first supporting member 21. Thereby,the wafer-attached structure 101 is formed.

The semiconductor wafer source 1 may be attached to the first supportingmember 21 by an adhesive agent. In a case in which the semiconductorwafer source 1 and the first supporting member 21 are made of the sametype of material (SiC), the semiconductor wafer source 1 may be bondedto the first supporting member 21 by a wafer direct bonding method. Thewafer direct bonding method may include a room temperature bondingmethod, a hydroxyl group bonding method or a plasma bonding method.

In the room temperature bonding method, first, ion beams are irradiatedonto each of the second main surface 3 of the semiconductor wafer source1 and the first supporting main surface 22 of the first supportingmember 21. Thereby, an atom with an atomic bonding is formed on each ofthe second main surface 3 of the semiconductor wafer source 1 and thefirst supporting main surface 22 of the first supporting member 21.Thereafter, the second main surface 3 of the semiconductor wafer source1 is attached to the first supporting main surface 22 of the firstsupporting member 21.

In the hydroxyl group bonding method, first, a hydrophilic treatment isperformed to each of the second main surface 3 of the semiconductorwafer source 1 and the first supporting main surface 22 of the firstsupporting member 21. An oxidizing chemical liquid such as sulfuricacid/hydrogen peroxide may be used in the hydrophilic treatment.Thereby, a hydroxyl group is introduced into each of the second mainsurface 3 of the semiconductor wafer source 1 and the first supportingmain surface 22 of the first supporting member 21. Thereafter, thesecond main surface 3 of the semiconductor wafer source 1 is attached tothe first supporting main surface 22 of the first supporting member 21.

In the plasma bonding method, first, an oxygen plasma treatment isperformed to each of the second main surface 3 of the semiconductorwafer source 1 and the first supporting main surface 22 of the firstsupporting member 21. Thereby, an active region is formed on each of thesecond main surface 3 of the semiconductor wafer source 1 and the firstsupporting main surface 22 of the first supporting member 21. The activeregion may include a hydroxyl group and/or an atom with an atomicbonding. Thereafter, the second main surface 3 of the semiconductorwafer source 1 is attached to the first supporting main surface 22 ofthe first supporting member 21.

In the wafer direct bonding method, a thermal treatment process and/or apressing process for increasing a bonding strength between thesemiconductor wafer source 1 and the first supporting member 21 may beperformed as necessary.

The wafer-attached structure 101 may include a bonding layer 28 whichbonds the semiconductor wafer source 1 and the first supporting member21 at a boundary region between the semiconductor wafer source 1 and thefirst supporting member 21. In a case in which the semiconductor wafersource 1 and the first supporting member 21 are attached by an adhesiveagent, the bonding layer 28 may include an adhesive agent.

In a case in which the semiconductor wafer source 1 and the firstsupporting member 21 are attached by the wafer direct bonding method,the bonding layer 28 may include a semiconductor bonding layer. Thesemiconductor bonding layer may have a crystalline state different froma crystalline state of the semiconductor wafer source 1 and/or acrystalline state of the first supporting member 21. The semiconductorbonding layer may include an amorphous layer. The amorphous layer mayhave a material of the semiconductor wafer source 1 and/or a material ofthe first supporting member 21.

Next, with reference to FIG. 3C, the semiconductor element 11 is formedin each of the plurality of element forming regions 10 set in the firstmain surface 2 of the semiconductor wafer source 1 (Step S3 of FIG. 2A).

A step of forming the semiconductor element 11 may include a step ofpolishing the first main surface 2 of the semiconductor wafer source 1.The step of forming the semiconductor element 11 may include a step offorming an epitaxial layer 29 on the first main surface 2 of thesemiconductor wafer source 1.

The step of forming the semiconductor element 11 may include a step ofselectively introducing n type impurities and/or p type impurities intothe epitaxial layer 29 depending on properties of the semiconductorelement 11. The step of forming the semiconductor element 11 may includea step of forming a first main surface electrode 30 on the epitaxiallayer 29.

In the polishing step, the first main surface 2 of the semiconductorwafer source 1 may be polished until an arithmetic average roughness Rabecomes not more than 1 nm. The polishing step may be performed by a CMP(Chemical Mechanical Polishing) method.

In the step of forming the epitaxial layer 29, SiC undergoes epitaxialgrowth from the first main surface 2 of the semiconductor wafer source1. The epitaxial layer 29 can be formed appropriately on the first mainsurface 2 of the semiconductor wafer source 1, if being formed after thepolishing step. Thereby, it is possible to appropriately form thesemiconductor element 11 in the first main surface 2 of thesemiconductor wafer source 1.

In the step of forming the first main surface electrode 30, the firstmain surface electrode 30 electrically connected to the element formingregion 10 is formed on each of the plurality of element forming regions10.

Next, with reference to FIG. 3D, a second supporting member 31 isattached to the semiconductor wafer source 1 (Step S4 of FIG. 2A). Thewafer-attached structure 101 may be handled in a state of having thesecond supporting member 31.

The second supporting member 31 supports the semiconductor wafer source1 from the first main surface 2 side of the semiconductor wafer source1. The second supporting member 31 may be attached to the semiconductorwafer source 1 via a double-sided adhesive tape 32.

Various types of materials can be applied to the second supportingmember 31 as long as they are able to support the semiconductor wafersource 1. For example, a member similar in structure to the firstsupporting member 21 may be adopted as the second supporting member 31.In this case, a description of the first supporting member 21 applies toa description of the second supporting member 31.

The second supporting member 31 may be a disc-shaped glass plate. Theglass plate may be similar in external shape to the first supportingmember 21. The second supporting member 31 may be directly attached tothe semiconductor wafer source 1 without use of the tape 32. In thiscase, the second supporting member 31 may be a single-sided adhesivetape.

The second supporting member 31 may be set such as to be equal to orlarger in planar area than the semiconductor wafer source 1 in view ofhandling convenience. In this case, the wafer-attached structure 101 hasa structure in which the semiconductor wafer source 1 is housed at aregion where the first supporting member 21 and the second supportingmember 31 face each other.

Thereby, the semiconductor wafer source 1 can be appropriately protectedfrom an external force, etc., by the first supporting member 21 and thesecond supporting member 31. Of course, the planar area of the secondsupporting member 31 may be less than or equal to the planar area of thesemiconductor wafer source 1.

Next, with reference to FIG. 3E, laser light is irradiated into thesemiconductor wafer source 1 from a laser light irradiation apparatus 33(Step S5 of FIG. 2A). Laser light is irradiated toward the semiconductorwafer source 1 in a state in which the semiconductor wafer source 1 issupported by the second supporting member 31. Laser light is irradiatedtoward the semiconductor wafer source 1 via the first supporting member21 from the second main surface 3 side of the semiconductor wafer source1.

A light collecting portion (a focal point) of laser light is set in athickness direction intermediate portion of the semiconductor wafersource 1. A distance W1 from the first main surface 2 of thesemiconductor wafer source 1 to the light collecting portion of laserlight is set according to thickness of a semiconductor device which isto be obtained. The distance W1 may be not less than 50 μm and not morethan 100 μm.

A laser light irradiation position to the semiconductor wafer source 1is moved along a horizontal direction parallel to the first main surface2 of the semiconductor wafer source 1. Thereby, a first altered layer34, the crystalline state of which is altered in properties differentfrom those of other regions, is formed in the thickness directionintermediate portion of the semiconductor wafer source 1.

The first altered layer 34 is formed in the thickness directionintermediate portion of the semiconductor wafer source 1 along ahorizontal direction. The first altered layer 34 is a laser processingtrace formed by irradiation of laser light. The first altered layer 34is also a layer in which a density, a refractive index, a mechanicalstrength (crystalline strength) and other physical characteristics aremodified different state from states of other regions due to alteration.

The first altered layer 34 may include at least any one of amelted-and-rehardened layer, a defect layer, a dielectric breakdownlayer and a refractive index change layer. The melted-and-rehardenedlayer is a layer in which the semiconductor wafer source 1 is partiallymelted and thereafter re-cured. The defect layer is a layer whichincludes vacancies, cracks, etc. The dielectric breakdown layer is alayer resulting from dielectric breakdown. The refractive index changelayer is a layer having a refractive index different from that ofanother region.

Next, with reference to FIG. 3F, the semiconductor wafer source 1 is cutalong a horizontal direction parallel to the first main surface 2 from athickness direction intermediate portion of the semiconductor wafersource 1 (Step S6 of FIG. 2A). More specifically, the semiconductorwafer source 1 is cleaved along the horizontal direction, with the firstaltered layer 34 as a starting point. The semiconductor wafer source 1is cleaved in a state in which the semiconductor wafer source 1 issupported by (held between) the first supporting member 21 and thesecond supporting member 31.

Thereby, the semiconductor wafer source 1 is separated into an elementformation wafer 41 having the semiconductor element 11 and an elementnon-formation wafer 42 free of the semiconductor element 11. The elementformation wafer 41 includes a first main surface 2 on one side and afirst cut surface 43 on the other side. The element formation wafer 41has a thickness Ta. The element non-formation wafer 42 includes a secondcut surface 44 on one side and the second main surface 3 on the otherside. The element non-formation wafer 42 has a thickness Tb.

With reference to FIG. 3G, after a step of separating the semiconductorwafer source 1, the first cut surface 43 of the element formation wafer41 is ground (Step S11 of FIG. 2B). The step of grinding the first cutsurface 43 may be performed by a CMP method.

The step of grinding the first cut surface 43 may be performed until theelement formation wafer 41 attains a desired thickness. That is, thestep of grinding the first cut surface 43 may include a step of thinningthe element formation wafer 41.

After the step of grinding the first cut surface 43, a second mainsurface electrode 45 is formed on the first cut surface 43 of theelement formation wafer 41 (Step S12 of FIG. 2B). Of course, the step ofgrinding the first cut surface 43 may be omitted. That is, the secondmain surface electrode 45 may be directly formed on the first cutsurface 43 immediately after the step of separating the semiconductorwafer source 1.

Thereafter, the element formation wafer 41 is cut along a dicing line 12(also refer to FIG. 1A and FIG. 1B) (Step S13 of FIG. 2B). Thereby, aplurality of semiconductor devices are cut out from the elementformation wafer 41.

The step of cutting the element formation wafer 41 may be performed in astate of being supported by the second supporting member 31. In thiscase, after the step of cutting the element formation wafer 41, thesecond supporting member 31 is removed. The step of cutting the elementformation wafer 41 may be performed after removal of the secondsupporting member 31.

After the step of separating the semiconductor wafer source 1, adetermination is made on whether the element non-formation wafer 42 isreusable as a new semiconductor wafer source (Step S7 of FIG. 2A).

The determination on whether the element non-formation wafer 42 isreusable may be made on the basis of the thickness Ta of the elementformation wafer 41 and the thickness Tb of the element non-formationwafer 42. In a case in which the thickness Tb of the elementnon-formation wafer 42 is not more than the thickness Ta of the elementformation wafer 41 (Tb≤Ta), a determination that it is not reusable maybe made. The non-reusable condition may be Tb<Ta.

The determination on whether the element non-formation wafer 42 isreusable may be made on the basis of a thickness Tch1 of a semiconductordevice which is to be obtained from the element non-formation wafer 42.In a case in which the thickness Tch1 of the semiconductor device whichis to be obtained is not less than the thickness Tb of the elementnon-formation wafer 42 (Tch1≥Tb), the determination that it is notreusable may be made. The non-reusable condition may be Tch1>Tb.

The condition that the element non-formation wafer 42 is not reusablemay include a case in which although the element non-formation wafer 42has a sufficient thickness Tb (for example, Tch1<Tb), a situation thatdoes not allow the reusable is occurred.

In a case in which the element non-formation wafer 42 is not reusable(Step S7 of FIG. 2A: NO), the method for manufacturing the semiconductordevice by using one semiconductor wafer source 1 is ended.

In a case in which the element non-formation wafer 42 is not reusable, astep of removing the element non-formation wafer 42 from the firstsupporting member 21 may be performed. The element non-formation wafer42 that is not reusable may be removed by a polishing process. Thepolishing process may be performed by a CMP method. After the removalstep, a step of reusing the first supporting member 21 as a supportingmember for supporting another semiconductor wafer source may beperformed.

With reference to FIG. 3H, in a case in which the element non-formationwafer 42 is reusable as a new semiconductor wafer source (Step S7 ofFIG. 2A: YES), a new semiconductor element 52 is formed in the elementnon-formation wafer 42 (Step S8 of FIG. 2A).

Hereinafter, the element non-formation wafer 42 is referred to as a “newsemiconductor wafer source 51.” The second cut surface 44 of the newsemiconductor wafer source 51 corresponds to the first main surface 2 ofthe semiconductor wafer source 1. The new semiconductor element 52 maybe formed on the second cut surface 44 of the new semiconductor wafersource 51 in a state in which the new semiconductor wafer source 51 issupported by the first supporting member 21.

The new semiconductor element 52 may be the same type as thesemiconductor element 11 described above or may be different therefrom.FIG. 3H shows a case that the new semiconductor element 52 is the sametype as the semiconductor element 11. The new semiconductor element 52is made into each of a plurality of element forming regions 10 set onthe second cut surface 44 of the new semiconductor wafer source 51.

The step of forming the new semiconductor element 52 may include a stepof polishing the second cut surface 44 of the new semiconductor wafersource 51. The step of forming the new semiconductor element 52 mayinclude a step of forming an epitaxial layer 29 on the second cutsurface 44 of the new semiconductor wafer source 51.

The step of forming the new semiconductor element 52 may include a stepof selectively introducing n type impurities and/or p type impuritiesinto the epitaxial layer 29 depending on properties of the newsemiconductor element 52. The step of forming the new semiconductorelement 52 may include a step of forming a first main surface electrode30 on the epitaxial layer 29.

In the polishing step, the second cut surface 44 of the newsemiconductor wafer source 51 may be polished until an arithmeticaverage roughness Ra becomes not more than 1 nm. The polishing step maybe performed by a CMP method.

In the step of forming the epitaxial layer 29, SiC undergoes epitaxialgrowth from the second cut surface 44 of the new semiconductor wafersource 51. The epitaxial layer 29 can be appropriately formed on thesecond cut surface 44 of the new semiconductor wafer source 51, if beingformed after the polishing step. Thereby, it is possible toappropriately form the new semiconductor element 52 in the second cutsurface 44 of the new semiconductor wafer source 51.

In the step of forming the first main surface electrode 30, the firstmain surface electrode 30 electrically connected to the element formingregion 10 is formed on each of the plurality of element forming regions10.

Next, with reference to FIG. 3I, the second supporting member 31 isattached to the new semiconductor wafer source 51 (Step S4 of FIG. 2A).The second supporting member 31 supports the semiconductor wafer source1 from the second cut surface 44 side of the new semiconductor wafersource 51. The second supporting member 31 may be attached to thesemiconductor wafer source 1 via a double-sided adhesive tape 32.

Next, with reference to FIG. 3J, laser light is irradiated toward thenew semiconductor wafer source 51 from a laser light irradiationapparatus 33 (Step S5 of FIG. 2A). Laser light is irradiated toward thenew semiconductor wafer source 51 in a state in which the newsemiconductor wafer source 51 is supported by the second supportingmember 31. Laser light is irradiated into the new semiconductor wafersource 51 via the first supporting member 21 from the second mainsurface 3 side of the new semiconductor wafer source 51.

A light collecting portion (a focal point) of laser light is set in athickness direction intermediate portion of the new semiconductor wafersource 51. A distance W2 from the second cut surface 44 of the newsemiconductor wafer source 51 to the light collecting portion of laserlight is set depending on the thickness Tch1 of the semiconductor devicewhich is to be obtained. The distance W2 may be not less than 50 μm andnot more than 100 μm.

A laser light irradiation position to the new semiconductor wafer source51 is moved along a horizontal direction parallel to the second cutsurface 44 of the new semiconductor wafer source 51. Thereby, a secondaltered layer 55, the crystalline state of which is altered inproperties different from those of the other regions, is formed in athickness direction intermediate portion of the new semiconductor wafersource 51.

The second altered layer 55 is formed in the thickness directionintermediate portion of the new semiconductor wafer source 51 along thehorizontal direction. The second altered layer 55 is approximatelysimilar in a structure to the previously described first altered layer34. A specific description of the second altered layer 55 will beomitted.

Next, with reference to FIG. 3K, anew semiconductor wafer source 51 iscut along the horizontal direction parallel to the second cut surface 44from a thickness direction intermediate portion of the new semiconductorwafer source 51 (Step S6 of FIG. 2A).

More specifically, the new semiconductor wafer source 51 is cleavedalong the horizontal direction, with the second altered layer 55 as astarting point. The new semiconductor wafer source 51 is cleaved in astate in which the new semiconductor wafer source 51 is supported by(held between) the first supporting member 21 and the second supportingmember 31.

Thereby, the new semiconductor wafer source 51 is separated into asecond element formation wafer 61 (element formed wafer) in which thenew semiconductor element 52 is formed and a second elementnon-formation wafer 62 in which the new semiconductor element 52 is notformed.

The second element formation wafer 61 includes a second cut surface 44on one side and a third cut surface 63 on the other side. The secondelement formation wafer 61 has a thickness Tc. The second elementnon-formation wafer 62 includes a fourth cut surface 64 on one side andthe second main surface 3 on the other side. The second elementnon-formation wafer 62 has a thickness Td.

After the step of separating the new semiconductor wafer source 51, thethird cut surface 63 of the second element formation wafer 61 is ground(Step S11 of FIG. 2B). The step of grinding the third cut surface 63 maybe performed by a CMP method.

The step of grinding the third cut surface 63 may be performed until thesecond element formation wafer 61 attains a desired thickness. That is,the step of grinding the third cut surface 63 may include a step ofthinning the second element formation wafer 61.

After the step of grinding the third cut surface 63, a second mainsurface electrode 45 is formed on the third cut surface 63 of the secondelement formation wafer 61 (Step S12 of FIG. 2B). Of course, the step ofgrinding the third cut surface 63 may be omitted. That is, the secondmain surface electrode 45 may be formed directly on the third cutsurface 63 immediately after the step of separating the newsemiconductor wafer source 51.

Thereafter, the second element formation wafer 61 is cut along a dicingline 12 (also refer to FIG. 1A and FIG. 1B) (Step S13 of FIG. 2B).Thereby, a plurality of semiconductor devices are cut out from thesecond element formation wafer 61.

The step of cutting the second element formation wafer 61 may beperformed in a state of being supported by the second supporting member31. In this case, after the step of cutting the second element formationwafer 61, the second supporting member 31 is removed. The step ofcutting the second element formation wafer 61 may be performed afterremoval of the second supporting member 31.

After the step of separating the new semiconductor wafer source 51, adetermination on whether the second element non-formation wafer 62 isreusable as a new semiconductor wafer source is made (Step S7 of FIG.2A).

The determination on whether the second element non-formation wafer 62is reusable may be made on the basis of the thickness Tc of the secondelement formation wafer 61 and the thickness Td of the second elementnon-formation wafer 62. In a case in which the thickness Td of thesecond element non-formation wafer 62 is not more than the thickness Tcof the second element formation wafer 61 (Td≤Tc), a determination thatit is not reusable may be made. The non-reusable condition may be Td<Tc.

The determination on whether the second element non-formation wafer 62is reusable may be made on the basis of a thickness Tch2 of asemiconductor device which is to be obtained from the second elementnon-formation wafer 62. In a case in which the thickness Tch2 of thesemiconductor device which is to be obtained is not less than athickness Td of the second element non-formation wafer 62 (Tch2≥Td), adetermination that it is not reusable may be made. The non-reusablecondition may be Tch2>Td.

The condition that the second element non-formation wafer 62 is notreusable may include a case in which although the second elementnon-formation wafer 62 has a sufficient thickness Td (for example,Tch2<Td), a situation that does not allow the reusable is occurred.

In a case in which the second element non-formation wafer 62 is notreusable as a new semiconductor wafer source (Step S7 of FIG. 2A: NO),the method for manufacturing the semiconductor device by using onesemiconductor wafer source 1 is ended.

In a case in which the second element non-formation wafer 62 is notreusable, there may be performed a step of removing the second elementnon-formation wafer 62 from the first supporting member 21. The secondelement non-formation wafer 62 which is not reusable may be removed by apolishing process. The polishing process may be performed by a CMPmethod. After the removal step, a step of reusing the first supportingmember 21 as a supporting member for supporting another semiconductorwafer source may be performed.

In a case in which the second element non-formation wafer 62 is reusableas a new semiconductor wafer source (Step S7 of FIG. 2A: YES), Step S8is performed. As described above, in this embodiment, the process ofStep S4 to Step S7 is repeated until the element non-formation wafer isto be not reusable as a new semiconductor wafer source.

As described above, in this embodiment, after the step of forming thesemiconductor element 11 (Step S3 of FIG. 2A), the step of separatingthe semiconductor wafer source 1 (Step S5 and Step S6 of FIG. 2A) isperformed. The step of separating the semiconductor wafer source 1 isperformed on the wafer-attached structure 101 in which the semiconductorwafer source 1 is attached to the first supporting member 21.

The semiconductor wafer source 1 is cleaved and separated into theelement formation wafer 41 and the element non-formation wafer 42. Inthis case, the element non-formation wafer 42 is in a state of beingattached to the first supporting member 21. Therefore, while theplurality of semiconductor devices can be cut out from the elementformation wafer 41, the element non-formation wafer 42 supported by thefirst supporting member 21 is reusable as the new semiconductor wafersource 51.

Thereby, it is possible to suppress a manufacturing delay and also anexcessive consumption of the semiconductor wafer source 1. Thus, it ispossible to provide the wafer-attached structure 101 capable ofefficiently consuming the semiconductor wafer source 1.

Further, in this embodiment, the new semiconductor element 52 is madeinto the new semiconductor wafer source 51 which is reused (Step S8 ofFIG. 2A). Still further, in this embodiment, the wafer source reuserepeating step in which the step of separating the semiconductor wafersource 1 and the step of reusing the semiconductor wafer source 1 arerepeated alternately is performed (Step S5 to Step S7 of FIG. 2A).Thereby, it is possible to increase the number of semiconductor devicesthat can be obtained from one semiconductor wafer source 1.

Further, in this embodiment, a step of cleaving the semiconductor wafersource 1 by using the laser light irradiation method in the step ofseparating the semiconductor wafer source 1 is performed (Step S5 andStep S6 of FIG. 2A). Thereby, it is not necessary to adjust thethickness of the semiconductor device by grinding the semiconductorwafer source 1. Thus, it is possible to suppress an increased costresulting from the grinding.

In particular, the laser light irradiation method is applicable to theSiC monocrystal semiconductor wafer source 1 which is relatively high inhardness. Further, the SiC monocrystal semiconductor wafer source 1 canbe appropriately separated into the element formation wafer 41 and theelement non-formation wafer 42.

The laser light irradiation method is also advantageous in that it ispossible to suppress an increased cost resulting from the grinding evenwhere the initial element non-formation wafer 42 is not reusable (StepS7 of FIG. 2A: NO). The laser light irradiation method is particularlyhelpful in the case of the SiC monocrystal semiconductor wafer source 1which is relatively high in hardness.

Further, in this embodiment, in the step of separating the semiconductorwafer source 1 (Step S5 and Step S6 of FIG. 2A), laser light isirradiated from the second main surface 3 side of the semiconductorwafer source 1 to the thickness direction intermediate portion of thesemiconductor wafer source 1.

No semiconductor element 11 is formed on the second main surface 3 ofthe semiconductor wafer source 1. Therefore, laser light can beirradiated with respect to the interior of the semiconductor wafersource 1 from the second main surface 3 side of the semiconductor wafersource 1 with few obstacles. Thereby, the first altered layer 34 and thesecond altered layer 55 can be appropriately formed on the semiconductorwafer source 1 to appropriately separate (cleave) the semiconductorwafer source 1.

In a case in which the second wafer edge portion 6 of the semiconductorwafer source 1 has a chamfered portion, a clearance is formed at aregion between the second wafer edge portion 6 of the semiconductorwafer source 1 and the first supporting main surface 22 of the firstsupporting member 21. Errors occurring at the light collecting portion(the focal point) of laser light include an error resulting from thisclearance.

Thus, in this embodiment, the second wafer edge portion 6 which is freeof a chamfered portion in the semiconductor wafer source 1 is formed.Thereby, it is possible to suppress the formation of a clearance at aregion between the second wafer edge portion 6 of the semiconductorwafer source 1 and the first supporting main surface 22 of the firstsupporting member 21.

Thus, it is possible to suppress an error occurring at the lightcollecting portion (the focal point) of laser light and, therefore,possible to appropriately form the first altered layer 34 inside thesemiconductor wafer source 1. As a result, the semiconductor wafersource 1 can be appropriately separated (cleaved) into the elementformation wafer 41 and the element non-formation wafer 42.

It is also possible to suppress an error occurring at the lightcollecting portion (the focal point) of laser light and, therefore,possible to appropriately form the second altered layer 55 inside thenew semiconductor wafer source 51. As a result, the new semiconductorwafer source 51 can be appropriately separated (cleaved) into a secondelement formation wafer 61 and a second element non-formation wafer 62.

In a case in which the first supporting member 21 is made of amonocrystal semiconductor wafer, etc., with which no impurities aredoped or which is low in concentrations of impurities, it is possible tosuppress absorption (attenuation) of laser light. Therefore,consideration is given to a material of the first supporting member 21,by which it is also possible to improve the quality of the first alteredlayer 34 formed in the semiconductor wafer source 1 and the quality ofthe second altered layer 55 formed in the new semiconductor wafer source51.

Further, in this embodiment, the melting point of the first supportingmember 21 is not less than the melting point of the semiconductor wafersource 1. Thereby, it is possible to suppress the melting anddeformation of the first supporting member 21 in the course ofmanufacture.

Further, in this embodiment, the ratio of the thermal expansioncoefficient of the supporting member in relation to the thermalexpansion coefficient of the semiconductor wafer source 1 is not lessthan 0.5 and not more than 1.5. Thereby, it is possible to reduce adifference in stress between a thermal stress occurring on thesemiconductor wafer source 1 (new semiconductor wafer source 51) sideand a thermal stress occurring on the first supporting member 21 side inthe course of manufacture. Thus, it is possible to suppress warping ofthe semiconductor wafer source 1 (new semiconductor wafer source 51).

In a case in which the first supporting member 21 is made of the sametype of material (SiC) as the semiconductor wafer source 1, the meltingpoint and the thermal expansion coefficient thereof are to be equal.Therefore, it is possible to reliably suppress the warping of thesemiconductor wafer source 1 (new semiconductor wafer source 51). It isalso possible to reliably suppress the melting and deformation of thefirst supporting member 21.

FIG. 4 is a process chart for describing the method for manufacturingthe semiconductor device according to the second preferred embodiment ofthe present invention. Hereinafter, a description of a stepcorresponding to the step described in the first preferred embodimentwill be omitted.

In this embodiment, in place of Step S1 to Step S3 (refer to FIG. 2A)according to the first preferred embodiment, Step S21 to Step S22 areperformed. More specifically, first, the semiconductor wafer source 1 inwhich the semiconductor element 11 is formed at each of the plurality ofelement forming regions 10 is prepared (Step S21 of FIG. 4).

Next, the semiconductor wafer source 1 in which the semiconductorelement 11 is formed is attached to a first supporting member 21 (StepS22 of FIG. 4). Thereby, the wafer-attached structure 101 is formed.Thereafter, Step S4 to Step S8 are performed.

As described above, in this embodiment, prior to the step of attachingthe semiconductor wafer source 1 to the first supporting member 21 (StepS22 of FIG. 4), the semiconductor element 11 is formed in thesemiconductor wafer source 1 (Step S21 of FIG. 4). Even with thismanufacturing method, the same effects as those described in the firstembodiment can be realized.

FIG. 5 is a process chart for describing the method for manufacturingthe semiconductor device according to the third preferred embodiment ofthe present invention. Hereinafter, a description of a stepcorresponding to the step described in the first preferred embodimentwill be omitted.

In this embodiment, in place of Step S1 to Step S3 (refer to FIG. 2A)according to the first preferred embodiment, Step S31 is performed. Morespecifically, first, the wafer-attached structure 101 is prepared (StepS31). The step of preparing the wafer-attached structure 101 may includea step of obtaining the wafer-attached structures 101 distributed inmarket.

The wafer-attached structure 101 may be manufactured through stepssimilar to Step S1 to Step S3 according to the first preferredembodiment (also refer to FIG. 2A). Thereafter, Step S4 to Step S8 areperformed. Even with this manufacturing method, the same effects asthose described in the first embodiment can be realized.

FIG. 6A is a process chart for describing the method for manufacturingthe semiconductor device according to the fourth preferred embodiment ofthe present invention. FIG. 6B is a process chart for describing a stepperformed on an element formation wafer 41 (new semiconductor wafersource 51) obtained from the step shown in FIG. 6A.

FIG. 7A to FIG. 7G are each a schematic cross sectional view fordescribing the manufacturing method shown in FIG. 6A and FIG. 6B.Hereinafter, a description of a step corresponding to the step describedin the first preferred embodiment will be omitted.

In this embodiment, in place of Step S1 to Step S3 (refer to FIG. 2A)according to the first preferred embodiment, Step S41 is performed.Further, in this embodiment, after Step S5 according to the firstpreferred embodiment and prior to Step S6, Step S42 is performed. Inthis embodiment, after Step S8, Step S43 is also performed.

More specifically, with reference to FIG. 7A, the semiconductor wafersource 1 in which the semiconductor element 11 is formed in a first mainsurface 2 is prepared (Step S41 of FIG. 6A). In this embodiment, asecond main surface 3 of the semiconductor wafer source 1 is exposedoutside. That is, no second main surface electrode 45 is formed on thesecond main surface 3 of the semiconductor wafer source 1.

Next, with reference to FIG. 7B, the second supporting member 31 isattached to the first main surface 2 side of the semiconductor wafersource 1 (Step S4 of FIG. 6A). The second supporting member 31 may beattached to the semiconductor wafer source 1 via the double-sidedadhesive tape 32.

Next, with reference to FIG. 7C, laser light is irradiated toward thesemiconductor wafer source 1 from the laser light irradiation apparatus33 (Step S5 of FIG. 6A). Laser light is irradiated toward the secondmain surface 3 of the semiconductor wafer source 1 in a state in whichthe semiconductor wafer source 1 is supported by the second supportingmember 31.

In this embodiment, laser light is directly irradiated into thethickness direction intermediate portion of the semiconductor wafersource 1 from the second main surface 3 side of the semiconductor wafersource 1. The distance W1 from the first main surface 2 of thesemiconductor wafer source 1 to the light collecting portion of laserlight is set depending on the thickness of the semiconductor devicewhich is to be obtained. The distance W1 may be not less than 50 μm andnot more than 100 μm.

The laser light irradiation position to the semiconductor wafer source 1is moved along a horizontal direction parallel to the first main surface2 of the semiconductor wafer source 1. Thereby, the first altered layer34, the crystalline state of which is altered in properties differentfrom those of other regions, is formed in the thickness directionintermediate portion of the semiconductor wafer source 1. In a case inwhich the semiconductor wafer source 1 includes an n⁺ type SiCsemiconductor substrate, the first altered layer 34 may be formed in theintermediate portion of the SiC semiconductor substrate.

In a case in which the semiconductor wafer source 1 has a chamferedportion at an edge portion thereof, an error will occur at the lightcollecting portion (the focal point) of laser light. Therefore, there isa possibility that the first altered layer 34 will not be formed such asto be parallel to the first main surface 2. Thus, in this embodiment,the semiconductor wafer source 1 which includes the second wafer edgeportion 6 which is free of being chamfered is prepared.

Thereby, it is possible to suppress an error occurring at the lightcollecting portion (the focal point) of laser light. As a result, thefirst altered layer 34 can be formed such as to be parallel to the firstmain surface 2 inside the semiconductor wafer source 1 across an entireregion of the semiconductor wafer source 1 in the thickness direction.Thus, it is possible to appropriately separate (cleave) thesemiconductor wafer source 1 into the element formation wafer 41 and theelement non-formation wafer 42.

Next, with reference to FIG. 7D, the semiconductor wafer source 1 havingthe first altered layer 34 is attached to the first supporting member 21(Step S42 of FIG. 6A). The semiconductor wafer source 1 is attached tothe first supporting member 21 in a posture that the second main surface3 faces a first supporting main surface 22 of the first supportingmember 21. Thereby, the wafer-attached structure 101 is formed. A methodfor attaching the semiconductor wafer source 1 to the first supportingmember 21 is as described in the first preferred embodiment and,therefore, a description thereof will be omitted.

Next, with reference to FIG. 7E, the semiconductor wafer source 1 is cutalong the horizontal direction parallel to the first main surface 2 fromthe thickness direction intermediate portion of the semiconductor wafersource 1 (Step S6 of FIG. 6A). More specifically, the semiconductorwafer source 1 is cleaved along the horizontal direction with the firstaltered layer 34 as a starting point.

The semiconductor wafer source 1 is cleaved in a state in which thesemiconductor wafer source 1 is supported by (held between) the firstsupporting member 21 and the second supporting member 31. Thereby, thesemiconductor wafer source 1 is separated into the element formationwafer 41 which has the semiconductor element 11 and the elementnon-formation wafer 42 which is free of the semiconductor element 11.

In the step of cutting the semiconductor wafer source 1 (Step S6 of FIG.6A), the semiconductor wafer source 1 only needs to be separated intothe element formation wafer 41 which has the semiconductor element 11and the element non-formation wafer 42 free of the semiconductor element11. In addition to a case that the semiconductor wafer source 1 which iscleaved as in this embodiment, for example, the first altered layer 34is adjusted for a position and a condition of formation so that thesemiconductor wafer source 1 may be separated by itself into the elementformation wafer 41 and the element non-formation wafer 42.

With reference to FIG. 7F, after the step of separating thesemiconductor wafer source 1, the first cut surface 43 of the elementformation wafer 41 is ground (Step S44 of FIG. 6B). The step of grindingthe first cut surface 43 may be performed by a CMP method.

The step of grinding the first cut surface 43 may be performed until theelement formation wafer 41 attains a desired thickness. That is, thestep of grinding the first cut surface 43 may include a step of thinningthe element formation wafer 41.

Next, with reference to FIG. 7G, the second main surface electrode 45 isformed on the first cut surface 43 of the element formation wafer 41(Step S45 of FIG. 6B). Of course, the step of grinding the first cutsurface 43 may be omitted. That is, the second main surface electrode 45may be directly formed on the first cut surface 43 immediately after thestep of separating the semiconductor wafer source 1.

After the step of grinding the element formation wafer 41 (Step S44 ofFIG. 6B) and prior to the step of forming the second main surfaceelectrode 45 (Step S45 of FIG. 6B), annealing treatment may be performedon the first cut surface 43 (ground surface) of the element formationwafer 41. Annealing treatment may be performed by a laser lightirradiation method. In this case, ohmic property of the second mainsurface electrode 45 in relation to the first cut surface 43 of theelement formation wafer 41 can be enhanced.

Thereafter, the element formation wafer 41 is cut along the dicing line12 (also refer to FIG. 1A and FIG. 1B) (Step S46 of FIG. 6B). Thereby, aplurality of semiconductor devices are cut out from the elementformation wafer 41.

The step of cutting the element formation wafer 41 may be performed inthe state of being supported by the second supporting member 31. In thiscase, after the step of cutting the element formation wafer 41, thesecond supporting member 31 is removed. The step of cutting the elementformation wafer 41 may be performed after removal of the secondsupporting member 31.

After the step of separating the semiconductor wafer source 1, adetermination on whether the element non-formation wafer 42 is reusableas the new semiconductor wafer source 51 is made (Step S7 of FIG. 6A).The way of the determination on whether the element non-formation wafer42 is reusable is as described in the first preferred embodiment and,therefore a description thereof will be omitted.

In a case in which the element non-formation wafer 42 is not reusable(Step S7 of FIG. 6A: NO), the method for manufacturing the semiconductordevice by using one semiconductor wafer source 1 is ended.

In a case in which the element non-formation wafer 42 is reusable as thenew semiconductor wafer source 51 (Step S7 of FIG. 6A: YES), the newsemiconductor element 52 is formed on the element non-formation wafer 42(Step S8 of FIG. 6A).

Next, the first supporting member 21 is removed from the newsemiconductor wafer source 51 (Step S43 of FIG. 6A). Thereby, the secondmain surface 3 of the new semiconductor wafer source 51 is exposedoutside. In a case in which the bonding layer 28 adheres on the secondmain surface 3 of the new semiconductor wafer source 51, the bondinglayer 28 is removed from the semiconductor wafer source 51.

The first supporting member 21 may be removed by a polishing process.The polishing process may be performed by a CMP method. The firstsupporting member 21 may be removed by an etching method. The firstsupporting member 21 may be removed by abrasion. In a case in which thefirst supporting member 21 is reusable, the first supporting member 21may be used as the supporting member for supporting anothersemiconductor wafer source. Thereafter, Step S4 is performed.

Then, a process of Step S4 to Step S7 is repeated until the elementnon-formation wafer is not reusable as a new semiconductor wafer sourceas with the first preferred embodiment. Even with this manufacturingmethod, the same effects as those described in the first embodiment canbe realized.

In this embodiment, a description has been made for an example in whichafter the step of forming the new semiconductor element 52 (Step S8 ofFIG. 6A), the step of removing the first supporting member 21 isperformed (Step S43 of FIG. 6A). However, the step of removing the firstsupporting member 21 (Step S43 of FIG. 6A) may be performed after thedetermination on whether the element non-formation wafer 42 is reusable(Step S7 of FIG. 6A) and prior to the step of forming the newsemiconductor element 52 (Step S8 of FIG. 6A).

FIG. 8A is a process chart for describing the method for manufacturingthe semiconductor device according to the fifth preferred embodiment ofthe present invention. FIG. 8B is a process chart for describing a stepperformed on an element formation wafer 41 (new semiconductor wafersource 51) obtained from the step shown in FIG. 8A.

FIG. 9A to FIG. 9M are each a schematic cross sectional view fordescribing the manufacturing method shown in FIG. 8A and FIG. 8B.Hereinafter, a description of a step corresponding to the step describedin the first preferred embodiment will be omitted.

In this embodiment, in place of Step S1 to Step S3 (refer to FIG. 2A)according to the first preferred embodiment, Step S51 is performed.Further, in this embodiment, after Step S5 according to the firstpreferred embodiment and prior to Step S6, Step S52 is performed.Further, in this embodiment, after Step S7 according to the firstpreferred embodiment, Step S53 to S56 or Steps S53, S57, S58 areperformed.

More specifically, with reference to FIG. 9A, the semiconductor wafersource 1 in which a semiconductor element 11 is formed on a first mainsurface 2 is prepared (Step S51 of FIG. 8A).

Next, with reference to FIG. 9B, a second supporting member 31 isattached to the first main surface 2 side of the semiconductor wafersource 1 (Step S4 of FIG. 8A). The second supporting member 31 may beattached to the semiconductor wafer source 1 via the double-sidedadhesive tape 32.

Next, with reference to FIG. 9C, laser light is irradiated from thelaser light irradiation apparatus 33 toward the semiconductor wafersource 1 (Step S5 of FIG. 8A). Laser light is irradiated toward thesecond main surface 3 of the semiconductor wafer source 1 in a state inwhich the semiconductor wafer source 1 is supported by the secondsupporting member 31.

In this embodiment, laser light is directly irradiated into thethickness direction intermediate portion of the semiconductor wafersource 1 from the second main surface 3 side of the semiconductor wafersource 1. The distance W1 from the first main surface 2 of thesemiconductor wafer source 1 to the light collecting portion of laserlight is set depending on the thickness of the semiconductor devicewhich is to be obtained. The distance W1 may be not less than 50 μm andnot more than 100 μm.

The laser light irradiation position to the semiconductor wafer source 1is moved along the horizontal direction parallel to the first mainsurface 2 of the semiconductor wafer source 1. Thereby, the firstaltered layer 34, the crystalline state of which is altered inproperties different from those of other regions, is formed in thethickness direction intermediate portion of the semiconductor wafersource 1. In a case in which the semiconductor wafer source 1 includesan n⁺ type SiC semiconductor substrate, the first altered layer 34 maybe formed at the intermediate portion of the SiC semiconductorsubstrate.

In a case in which the semiconductor wafer source 1 has a chamferedportion at an edge portion thereof, an error will occur at a lightcollecting portion (a focal point) of laser light and, therefore, thereis a possibility that the first altered layer 34 will not be formed suchas to be parallel to the first main surface 2. Thus, in this embodiment,the semiconductor wafer source 1 which includes the second wafer edgeportion 6 that is free of being chamfered is prepared.

Thereby, it is possible to suppress an error occurring at the lightcollecting portion (the focal point) of laser light. As a result, thefirst altered layer 34 can be formed inside the semiconductor wafersource 1 across an entire region of the semiconductor wafer source 1 inthe thickness direction such as to be parallel to the first main surface2. Thus, it is possible to appropriately separate (cleave) thesemiconductor wafer source 1 into the element formation wafer 41 and theelement non-formation wafer 42.

Next, with reference to FIG. 9D, the semiconductor wafer source 1 havingthe first altered layer 34 is attached to a first supporting member 21(Step S52 of FIG. 8A). The semiconductor wafer source 1 is attached tothe first supporting member 21 in a posture that the second main surface3 faces the first supporting main surface 22 of the first supportingmember 21. Thereby, the wafer-attached structure 101 is formed. Themethod for attaching the semiconductor wafer source 1 to the firstsupporting member 21 is as described in the first preferred embodimentand, therefore, a description thereof will be omitted.

Next, with reference to FIG. 9E, the semiconductor wafer source 1 is cutalong the horizontal direction parallel to the first main surface 2 fromthe thickness direction intermediate portion of the semiconductor wafersource 1 (Step S6 of FIG. 8A). More specifically, the semiconductorwafer source 1 is cleaved along the horizontal direction with the firstaltered layer 34 as a starting point.

The semiconductor wafer source 1 is cleaved in a state in which thesemiconductor wafer source 1 is supported by (held between) the firstsupporting member 21 and the second supporting member 31. Thereby, thesemiconductor wafer source 1 is separated into the element formationwafer 41 having the semiconductor element 11 and the elementnon-formation wafer 42 free of the semiconductor element 11.

In a step of cutting the semiconductor wafer source 1 (Step S6 of FIG.6A), the semiconductor wafer source 1 only needs to be separated intothe element formation wafer 41 having the semiconductor element 11 andthe element non-formation wafer 42 free of the semiconductor element 11.In addition to a case that the semiconductor wafer source 1 is cleavedas in this embodiment, for example, the first altered layer 34 isadjusted for a position and a condition of the formation so that thesemiconductor wafer source 1 can be by itself separated into the elementformation wafer 41 and the element non-formation wafer 42.

With reference to FIG. 9F, after the step of separating thesemiconductor wafer source 1, the first cut surface 43 of the elementformation wafer 41 is ground (Step S59 of FIG. 8B). The step of grindingthe first cut surface 43 may be performed by a CMP method.

The step of grinding the first cut surface 43 may be performed until theelement formation wafer 41 attains a desired thickness. That is, thestep of grinding the first cut surface 43 may include a step of thinningthe element formation wafer 41.

Next, with reference to FIG. 9G, the second main surface electrode 45 isformed on the first cut surface 43 of the element formation wafer 41(Step S60 of FIG. 8B). Of course, the step of grinding the first cutsurface 43 may be omitted. That is, the second main surface electrode 45may be directly formed on the first cut surface 43 immediately after thestep of separating the semiconductor wafer source 1.

After the step of grinding the element formation wafer 41 (Step S44 ofFIG. 6B) and prior to the step of forming the second main surfaceelectrode 45 (Step S45 of FIG. 6B), annealing treatment may be performedon the first cut surface 43 (ground surface) of the element formationwafer 41. Annealing treatment may be performed by a laser lightirradiation method. In this case, ohmic property of the second mainsurface electrode 45 in relation to the first cut surface 43 of theelement formation wafer 41 can be enhanced.

Thereafter, the element formation wafer 41 is cut along the dicing line12 (also refer to FIG. 1A and FIG. 1B) (Step S61 of FIG. 8B). Thereby, aplurality of semiconductor devices are cut out from the elementformation wafer 41.

The step of cutting the element formation wafer 41 may be performed inthe state of being supported by the second supporting member 31. In thiscase, after the step of cutting the element formation wafer 41, thesecond supporting member 31 is removed. The step of cutting the elementformation wafer 41 may be performed after removal of the secondsupporting member 31.

After the step of separating the semiconductor wafer source 1, thedetermination on whether the element non-formation wafer 42 is reusableas the new semiconductor wafer source 51 is made (Step S7 of FIG. 8A).In a case in which the element non-formation wafer 42 is not reusable(Step S7 of FIG. 8A: NO), the method for manufacturing the semiconductordevice by using one semiconductor wafer source 1 is ended. The way ofthe determination on whether the element non-formation wafer 42 isreusable is as described in the first preferred embodiment and,therefore a description thereof will be omitted.

In a case in which the element non-formation wafer 42 is reusable as thenew semiconductor wafer source 51 (Step S7 of FIG. 8A: YES), adetermination on whether the element non-formation wafer 42 cannot bedivided again and also on whether it can be used as a last semiconductorwafer source is made (Step S53 of FIG. 8A). The determination on whetherthe element non-formation wafer 42 can be divided again may be made onthe basis of the thickness of a semiconductor device which is to beobtained.

In a case in which the element non-formation wafer 42 cannot be dividedand has such a thickness that it can be made equal in thickness to asemiconductor device by a short-time grinding, a determination that itcan be used as the last semiconductor wafer source may be made. Further,in a case in which the element non-formation wafer 42 cannot be dividedand has such a thickness that it is substantially equal in thickness toa semiconductor device which is to be obtained, a determination that itcan be used as the last semiconductor wafer source may be made.

With reference to FIG. 9H, in a case in which the element non-formationwafer 42 cannot be divided and can be used as the last semiconductorwafer source (Step S53 of FIG. 8A: YES), the element non-formation wafer42 is reused as a last semiconductor wafer source 81.

Then, the first supporting member 21 is removed from the lastsemiconductor wafer source 81 (Step S54 of FIG. 8A). Thereby, the secondmain surface 3 of the last semiconductor wafer source 81 is exposedoutside.

The first supporting member 21 may be removed by a polishing process.The polishing process may be performed by a CMP method. The firstsupporting member 21 may be removed by an etching method. The firstsupporting member 21 may be removed by abrasion. In a case in which thefirst supporting member 21 is reusable, the first supporting member 21may be used as a supporting member for supporting another semiconductorwafer source.

Next, with reference to FIG. 9I, in a case in which the bonding layer 28adheres on the second main surface 3 of the last semiconductor wafersource 81, the bonding layer 28 is removed from the last semiconductorwafer source 81.

Next, with reference to FIG. 9J, the new semiconductor element 52 isformed on the second cut surface 44 of the last semiconductor wafersource 81 (Step S55 of FIG. 8A). The new semiconductor element 52 may bethe same type as the previously described semiconductor element 11 ormay be different therefrom.

FIG. 9J shows an example in which the new semiconductor element 52 isthe same type as the semiconductor element 11. The new semiconductorelement 52 is formed in each of the plurality of element forming regions10 set on the second cut surface 44 of the last semiconductor wafersource 81. The step of forming the new semiconductor element 52 is asdescribed in the first preferred embodiment and, therefore, adescription thereof will be omitted. Then, the second main surfaceelectrode 45 is formed on the second main surface 3 of the lastsemiconductor wafer source 81.

Prior to the step of forming the second main surface electrode 45,annealing treatment may be performed on the second main surface 3(ground surface) of the last semiconductor wafer source 81. Annealingtreatment may be performed by a laser light irradiation method. In thiscase, ohmic property of the second main surface electrode 45 in relationto the second main surface 3 of the last semiconductor wafer source 81can be enhanced.

Thereafter, the last semiconductor wafer source 81 is cut along thedicing line 12 (also refer to FIG. 1A and FIG. 1B) (Step S13 of FIG.2B). Thereby, a plurality of semiconductor devices are cut out from thelast semiconductor wafer source 81.

On the other hand, with reference to FIG. 9K, in a case in which theelement non-formation wafer 42 can be divided again and cannot be usedas the last semiconductor wafer source (Step S53 of FIG. 8A: NO), theelement non-formation wafer 42 is reused as the new semiconductor wafersource 51.

Then, the first supporting member 21 is removed from the newsemiconductor wafer source 51 (Step S57 of FIG. 8A). Thereby, the secondmain surface 3 of the new semiconductor wafer source 51 is exposedoutside.

The first supporting member 21 may be removed by a polishing process.The polishing process may be performed by a CMP method. The firstsupporting member 21 may be removed by an etching method. The firstsupporting member 21 may be removed by abrasion. In a case in which thefirst supporting member 21 is reusable, the first supporting member 21may be used as a supporting member for supporting another semiconductorwafer source.

Next, with reference to FIG. 9L, in a case in which the bonding layer 28adheres on the second main surface 3 of the new semiconductor wafersource 51, the bonding layer 28 is removed from the new semiconductorwafer source 51.

Next, with reference to FIG. 9M, the new semiconductor element 52 isformed on the second cut surface 44 of the new semiconductor wafersource 51 (Step S58 of FIG. 8A). The new semiconductor element 52 may bethe same type as the previously described semiconductor element 11 ormay be different therefrom.

FIG. 9M shows an example in which the new semiconductor element 52 isthe same type as the semiconductor element 11. The new semiconductorelement 52 is formed in each of the plurality of element forming regions10 set on the second cut surface 44 of the new semiconductor wafersource 51. The step of forming the new semiconductor element 52 is asdescribed in the first preferred embodiment and, therefore, adescription thereof will be omitted.

As described above, in this embodiment, the step of Step S4 to Step S7is repeated until the element non-formation wafer is not reusable as thenew semiconductor wafer source. Further, in this embodiment, a processof Step S4 to Step S53 is repeated until the element non-formation wafercan be the last semiconductor wafer source.

Even with this manufacturing method, the same effects as those describedin the first embodiment can be realized. In particular, in the presentpreferred embodiment, the element non-formation wafer 42 is reusable asthe last semiconductor wafer source 81 (Step S53 to Step S56). Thereby,an initial semiconductor wafer source 1 can be consumed without beingwasted.

In this process, a description has been made for an example in which thestep of forming the new semiconductor element 52 in the lastsemiconductor wafer source 81 (Step S55 of FIG. 8A) is performed afterthe step of removing the first supporting member 21 (Step S54 of FIG.8A). However, the step of forming the new semiconductor element 52 (StepS55 of FIG. 8A) may be performed prior to the step of removing the firstsupporting member 21 (Step S54 of FIG. 8A).

In this process, a description has been made for an example in which thestep of forming the new semiconductor element 52 in the newsemiconductor wafer source 51 (Step S58 of FIG. 8A) is performed afterthe step of removing the first supporting member 21 (Step S57 of FIG.8A). However, the step of forming the new semiconductor element 52 (StepS58 of FIG. 8A) may be performed prior to the step of removing the firstsupporting member 21 (Step S57 of FIG. 8A).

FIG. 10 is a cross sectional view which shows a semiconductor device 111according to one example of the present invention.

With reference to FIG. 10, the semiconductor device 111 includes aSchottky barrier diode as one example of the semiconductor element 11.The semiconductor device 111 includes a chip-shaped SiC semiconductorlayer 112. The SiC semiconductor layer 112 has a first main surface 113on one side, a second main surface 114 on the other side and a sidesurface 115 connecting the first main surface 113 and the second mainsurface 114.

In this mode, the SiC semiconductor layer 112 has a laminated structurewhich includes an n⁺ type SiC semiconductor substrate 116 and an n typeSiC epitaxial layer 117. An n type impurity concentration of the SiCepitaxial layer 117 is less than an n type impurity concentration of theSiC semiconductor substrate 116.

The SiC semiconductor substrate 116 forms the second main surface 114 ofthe SiC semiconductor layer 112. The SiC epitaxial layer 117 forms thefirst main surface 113 of the SiC semiconductor layer 112. The SiCsemiconductor substrate 116 and the SiC epitaxial layer 117 form theside surface 115 of the SiC semiconductor layer 112.

A diode region 118 of n type is formed at a surface layer portion of thefirst main surface 113 of the SiC semiconductor layer 112. In this mode,the diode region 118 is formed at a central portion of the first mainsurface 113 of the SiC semiconductor layer 112 in a plan view as viewedin a normal direction of the first main surface 113 of the SiCsemiconductor layer 112 (hereinafter, simply referred to as a “planview”). In this mode, the diode region 118 is formed by using a part ofthe SiC epitaxial layer 117.

A guard region 119 of p⁺ type is formed at the surface layer portion ofthe first main surface 113 of the SiC semiconductor layer 112. The guardregion 119 is formed in a band shape extending along the diode region118 in plan view. More specifically, the guard region 119 is formed inan endless shape surrounding the diode region 118 in plan view (forexample, a quadrilateral annular shape, a quadrilateral annular shape, acorner of which is chamfered, or a circular annular shape). Thereby, theguard region 119 is formed as a guard ring region.

P type impurities of the guard region 119 may not be activated. In thiscase, the guard region 119 is formed as a non-semiconductor region. Thep type impurities of the guard region 119 may be activated. In thiscase, the guard region 119 is formed as a semiconductor region of ptype.

An insulation layer 120 is formed on the first main surface 113 of theSiC semiconductor layer 112. An opening 121 for exposing the dioderegion 118 is formed on the insulation layer 120. In this mode, inaddition to the diode region 118, an inner peripheral edge of the guardregion 119 is also exposed from the opening 121.

A first main surface electrode 30 is formed on the insulation layer 120.The first main surface electrode 30 enters into the opening 121 on theinsulation layer 120. The first main surface electrode 30 iselectrically connected to the diode region 118 inside the opening 121.

The first main surface electrode 30 forms a Schottky junction with thediode region 118. Thereby, a Schottky barrier diode having the firstmain surface electrode 30 served as an anode and the diode region 118served as a cathode is formed.

A second main surface electrode 45 is formed on the second main surface114 of the SiC semiconductor layer 112. The second main surfaceelectrode 45 forms an ohmic contact with the second main surface 114 ofthe SiC semiconductor layer 112.

FIG. 11A is a process chart for describing the method for manufacturingthe semiconductor device according to the sixth preferred embodiment ofthe present invention. FIG. 11B is a process chart for describing a stepperformed on the element formation wafer 41 which is obtained from astep shown in FIG. 11A.

FIG. 12A to FIG. 12I are each a schematic cross sectional view fordescribing the manufacturing method shown in FIG. 11A and FIG. 11B byapplying the manufacturing method shown in FIG. 11A and FIG. 11B to themethod for manufacturing the semiconductor device 111 shown in FIG. 10.

Hereinafter, a description of a step corresponding to the step describedin the first preferred embodiment will be omitted. In FIG. 12A to FIG.12I, for the sake of convenience of description, only a region in whichone semiconductor device 111 is formed is shown, and regions of othersemiconductor devices and an end region of the semiconductor wafersource 1 are omitted.

In this embodiment, in place of Step S1 to Step S5 (refer to FIG. 2A)according to the first preferred embodiment, Step S71 to Step S74 areperformed. Further, in this embodiment, after Step S7 according to thefirst preferred embodiment, Step S75 is performed.

More specifically, first, with reference to FIG. 12A, the semiconductorwafer source 1 made of an n⁺ type SiC monocrystal is prepared. Next,portions of the semiconductor element 11 are formed on the first mainsurface 2 of the semiconductor wafer source 1 (Step S71 of FIG. 11A).

In this embodiment, the step of forming the portions of thesemiconductor element 11 includes a step of forming the n type SiCepitaxial layer 117 on the first main surface 2 of the semiconductorwafer source 1. Further, the step of forming the portions of thesemiconductor element 11 includes a step of forming the diode region 118of the n type and a guard region 119 of the p⁺ type in the surface layerportion of the SiC epitaxial layer 117.

In the step of forming the SiC epitaxial layer 117, SiC undergoesepitaxial growth from the first main surface 2 of the semiconductorwafer source 1. The diode region 118 is formed by using a part of theSiC epitaxial layer 117.

Next, with reference to FIG. 12B, the semiconductor wafer source 1 inwhich the portions of the semiconductor element 11 are formed isattached to the first supporting member 21 (Step S72 of FIG. 11A). Thesemiconductor wafer source 1 is attached to the first supporting member21 in a posture that the second main surface 3 faces a first supportingmain surface 22 of the first supporting member 21. Thereby, thewafer-attached structure 101 is formed. The method for attaching thesemiconductor wafer source 1 to the first supporting member 21 is asdescribed in the first preferred embodiment and, therefore, adescription thereof will be omitted.

Next, with reference to FIG. 12C, laser light is irradiated toward thesemiconductor wafer source 1 from the laser light irradiation apparatus33 (Step S73 of FIG. 11A). In this embodiment, laser light is irradiatedfrom the first main surface 2 side of the semiconductor wafer source 1to the thickness direction intermediate portion of the semiconductorwafer source 1.

In this step, no electrode layer is formed on a surface of the SiCepitaxial layer 117 on the first main surface 2 side of thesemiconductor wafer source 1. Further, no insulation layer is formedeither on the surface of the SiC epitaxial layer 117 on the first mainsurface 2 side of the semiconductor wafer source 1. Therefore, it ispossible to irradiate laser light with respect to an interior of thesemiconductor wafer source 1 from the first main surface 2 side of thesemiconductor wafer source 1 with few obstacles.

The distance W1 from the first main surface 2 of the semiconductor wafersource 1 to the light collecting portion of laser light is set dependingon the thickness of a semiconductor device which is to be obtained. Thedistance W1 may be not less than 50 μm and not more than 100 μm.

The laser light irradiation position to the semiconductor wafer source 1is moved along the horizontal direction parallel to the first mainsurface 2 of the semiconductor wafer source 1. Thereby, the firstaltered layer 34, the crystalline state of which is altered inproperties different from those of other regions, is formed in thethickness direction intermediate portion of the semiconductor wafersource 1. The first altered layer 34 may be formed in the intermediateportion of the n⁺ type semiconductor wafer source 1.

In a case in which the semiconductor wafer source 1 has a chamferedportion at an edge portion thereof, an error will occur at a lightcollecting portion (a focal point) of laser light. Therefore, there is apossibility that the first altered layer 34 will not be formed such asto be parallel to the first main surface 2. Thus, in this embodiment,the semiconductor wafer source 1 which includes the second wafer edgeportion 6 that is not chamfered is prepared.

Thereby, it is possible to suppress an error occurring at the lightcollecting portion (the focal point) of laser light. As a result, thefirst altered layer 34 can be formed inside the semiconductor wafersource 1 across an entire region of the semiconductor wafer source 1 inthe thickness direction such as to be parallel to the first main surface2. Thereby, it is possible to appropriately separate (cleave) thesemiconductor wafer source 1 into an element formation wafer 41 and anelement non-formation wafer 42.

Next, with reference to FIG. 12D, a second supporting member 31 isattached to the first main surface 2 of the semiconductor wafer source 1(Step S74 of FIG. 11A). The second supporting member 31 may be attachedto the semiconductor wafer source 1 via the double-sided adhesive tape32.

Next, with reference to FIG. 12E, the semiconductor wafer source 1 iscut along a horizontal direction parallel to the first main surface 2from a thickness direction intermediate portion of the semiconductorwafer source 1 (Step S6 of FIG. 11A). More specifically, thesemiconductor wafer source 1 is cleaved along the horizontal directionwith the first altered layer 34 as a starting point.

The semiconductor wafer source 1 is cleaved in a state in which thesemiconductor wafer source 1 is supported by (held between) the firstsupporting member 21 and the second supporting member 31. Thereby, thesemiconductor wafer source 1 is separated into the element formationwafer 41 having the portions of the semiconductor element 11 and theelement non-formation wafer 42 free of the semiconductor element 11.

In the step of cutting the semiconductor wafer source 1 (Step S6 of FIG.11A), the semiconductor wafer source 1 needs only to be separated intothe element formation wafer 41 having the semiconductor element 11 andthe element non-formation wafer 42 free of the semiconductor element 11.In addition to a case that the semiconductor wafer source 1 is cleavedas in this embodiment, for example, the first altered layer 34 isadjusted for a position and a condition of the formation so that thesemiconductor wafer source 1 can be separated by itself into the elementformation wafer 41 and the element non-formation wafer 42.

With reference to FIG. 12F, after the step of separating thesemiconductor wafer source 1, the first cut surface 43 of the elementformation wafer 41 is ground (Step S76 of FIG. 11B). The step ofgrinding the first cut surface 43 may be performed by a CMP method.

The step of grinding the first cut surface 43 may be performed until theelement formation wafer 41 attains a desired thickness. That is, thestep of grinding the first cut surface 43 may include a step of thinningthe element formation wafer 41.

Next, with reference to FIG. 12G, the second main surface electrode 45is formed on the first cut surface 43 of the element formation wafer 41(Step S77 of FIG. 11B). Of course, the step of grinding the first cutsurface 43 may be omitted. That is, the second main surface electrode 45may be directly formed on the first cut surface 43 immediately after astep of separating the semiconductor wafer source 1.

After the step of grinding the element formation wafer 41 (Step S76 ofFIG. 11B) and prior to the step of forming the second main surfaceelectrode 45 (Step S77 of FIG. 11B), annealing treatment may beperformed on the first cut surface 43 (ground surface) of the elementformation wafer 41. Annealing treatment may be performed by the laserlight irradiation method. In this case, the second main surfaceelectrode 45 can be enhanced in Ohmic property in relation to the firstcut surface 43 of the element formation wafer 41.

Next, with reference to FIG. 12H, the second supporting member 31 isremoved from the first main surface 2 of the semiconductor wafer source1 (Step S78 of FIG. 11B). The step of removing the second supportingmember 31 may be performed prior to the step of grinding the first cutsurface 43 or the step of forming the second main surface electrode 45.

Next, with reference to FIG. 12I, the rest portions of the semiconductorelement 11 are formed on the first main surface 2 of the semiconductorwafer source 1 (Step S79 of FIG. 11B). In this embodiment, theinsulation layer 120 and the first main surface electrode 30 are formedon the first main surface 2 of the semiconductor wafer source 1 as therest portions of the semiconductor element 11.

Thereafter, the element formation wafer 41 is cut along the dicing line12 (also refer to FIG. 1A and FIG. 1B) (Step S80 of FIG. 11B). Thereby,the plurality of semiconductor devices 111 are cut out from the elementformation wafer 41.

After the step of separating the semiconductor wafer source 1, thedetermination on whether the element non-formation wafer 42 is reusableas the new semiconductor wafer source 51 is made (Step S7 of FIG. 11A).The way of the determination on whether the element non-formation wafer42 is reusable is as described in the first preferred embodiment and,therefore, a description thereof will be omitted.

In a case in which the element non-formation wafer 42 is not reusable(Step S7 of FIG. 11A: NO), the method for manufacturing thesemiconductor device by using one semiconductor wafer source 1 is ended.

In a case in which the element non-formation wafer 42 is reusable as thenew semiconductor wafer source 51 (Step S7 of FIG. 11A: YES), as withStep S71, portions of the semiconductor element 52 are formed in theelement non-formation wafer 42 (the new semiconductor wafer source 51)(Step S75 of FIG. 11A).

The step of forming the portions of the semiconductor element 52 (StepS75 of FIG. 11A) may be performed in a state in which the newsemiconductor wafer source 51 is attached to the supporting member 21.Of course, prior to the step of forming the portions of thesemiconductor element 52 (Step S75 of FIG. 11A), the first supportingmember 21 may be removed. In this case, after the step of partiallyforming the new semiconductor element 52 (Step S75 of FIG. 11A), thesupporting member 21 may be attached again to the new semiconductorwafer source 51.

Thereafter, Step S73 is performed. As described above, in thisembodiment, the step of Step S73 to Step S7 is repeated until theelement non-formation wafer is not reusable as the new semiconductorwafer source. Even with this manufacturing method, the same effects asthose described in the first embodiment can be realized.

In this embodiment, a description has been made for an example in whichthe Schottky barrier diode is formed as an example of the semiconductorelement 11. However, the semiconductor element 11 may include afunctional element different from the Schottky barrier diode. Asdescribed in the first preferred embodiment, the semiconductor element11 may include at least any one of the semiconductor rectifier element,the semiconductor switching element and the semiconductor passiveelement.

The preferred embodiments of the present invention are described, andthe present invention can be implemented in other modes.

In each of the preferred embodiments described above, the wafer-attachedstructure 101 shown in FIG. 13 may be adopted. FIG. 13 is a crosssectional view which shows a first modification example of thewafer-attached structure 101. Hereinafter, a description on aconstitution corresponding to the constitution described in the firstpreferred embodiment will be omitted.

With reference to FIG. 13, in the wafer-attached structure 101 accordingto the present modification example, the first wafer edge portion 5 ofthe semiconductor wafer source 1 has a chamfered portion. The firstwafer edge portion 5 may have a C-chamfered portion which isC-chamfered. The first wafer edge portion 5 may have an R-chamferedportion which is R-chamfered.

On the other hand, the second wafer edge portion 6 of the semiconductorwafer source 1 has no chamfered portion. Thereby, it is possible tosuppress the formation of a clearance at a region between the secondwafer edge portion 6 of the semiconductor wafer source 1 and the firstsupporting main surface 22 of the first supporting member 21 in thestate in which the semiconductor wafer source 1 is supported by thefirst supporting member 21.

As a result, it is possible to suppress an error occurring at a lightcollecting portion (a focal point) of laser light irradiated to aninterior of the semiconductor wafer source 1. As described above, evenwith the wafer-attached structure 101 according to the presentmodification example, the same effects as those described in the firstembodiment can be realized.

In each of the previously described preferred embodiments, thewafer-attached structure 101 shown in FIG. 14 may be adopted. FIG. 14 isa cross sectional view which shows a second modification example of thewafer-attached structure 101. Hereinafter, a description on aconstitution corresponding to the constitution described in the firstpreferred embodiment will be omitted.

With reference to FIG. 14, in the wafer-attached structure 101 accordingto the present modification example, in place of the first orientationflat 7, a first orientation notch 71 (first mark) which indicates acrystal orientation, etc., is formed on the semiconductor wafer source1.

The first orientation notch 71 includes a notched portion formed at aperipheral edge of the semiconductor wafer source 1. The firstorientation notch 71 includes a recessed portion which is recessedtoward the central portion of the semiconductor wafer source 1 at aperipheral edge of the semiconductor wafer source 1.

Further, in the wafer-attached structure 101 according to the presentmodification example, in place of the second orientation flat 27, asecond orientation notch 72 (second mark) which indicates a crystalorientation, etc., is formed in the first supporting member 21.

The second orientation notch 72 includes a notched portion which isformed at a peripheral edge of the first supporting member 21. Thesecond orientation notch 72 includes a recessed portion which isrecessed toward the central portion of the first supporting member 21 atthe peripheral edge of the first supporting member 21.

The second orientation notch 72 of the first supporting member 21 mayindicate a crystal orientation which is equal to a crystal orientationof the first orientation notch 71 of the semiconductor wafer source 1.Thereby, the semiconductor wafer source 1 can be attached to the firstsupporting member 21, with the crystal orientation understood.

The second orientation notch 72 of the first supporting member 21 may bepositionally aligned with the first orientation notch 71 of thesemiconductor wafer source 1. That is, the second orientation notch 72may face the first orientation notch 71 at a position proximate to thefirst orientation notch 71.

Thereby, the crystal orientation of the semiconductor wafer source 1 isin agreement with the crystal orientation of the first supporting member21. Thus, it is possible to easily determine the crystal orientation ofthe semiconductor wafer source 1. Thereby, the semiconductor wafersource 1 can be handled more conveniently.

As described above, even with the wafer-attached structure 101 accordingto the present modification example, the same effects as those describedin the first embodiment can be realized.

Of course, while the semiconductor wafer source 1 has the firstorientation flat 7, the first supporting member 21 may have the secondorientation notch 72. Further, while the semiconductor wafer source 1has the first orientation notch 71, the first supporting member 21 mayhave the second orientation flat 27.

In each of the preferred embodiments described above, in place of thesemiconductor wafer source 1 made of the SiC monocrystal, thesemiconductor wafer source 1 made of an Si (silicon) monocrystal. Inthis case, the thickness T1 of the semiconductor wafer source 1 may benot less than 100 μm and not more than 1000 μm. The thickness T1 of thesemiconductor wafer source 1 may be not less than 500 μm and not morethan 800 μm.

In a case in which the semiconductor wafer source 1 made of an Simonocrystal is adopted, the first supporting member 21 preferablyincludes a semiconductor wafer made of Si monocrystal. Thereby, physicalproperties of the first supporting member 21 are substantially equal tothose of the semiconductor wafer source 1.

The thickness T2 of the first supporting member 21 may be not less than100 μm and not more than 1000 μm. Specifically, the thickness T2 of thefirst supporting member 21 is not less than 500 μm and not more 800 μm.The thickness T2 of the first supporting member 21 may be equal to thethickness T1 of the semiconductor wafer source 1.

A description of configurations of the first supporting member 21according to the first preferred embodiment is also applicable to a casein which the first supporting member 21 is made of the Si monocrystalsemiconductor wafer.

Si is lower in hardness than SiC. For this reason, difficulty inprocessing the Si monocrystal semiconductor wafer source 1 is lower thandifficulty in processing the SiC monocrystal semiconductor wafer source1. Thus, even with the semiconductor wafer source 1 made of Simonocrystal, the same effects as those described in the first embodimentcan be realized.

Of course, in each of the preferred embodiments described above, thefirst supporting member 21 may include a substrate (wafer) made of amaterial other than a semiconductor wafer. For example, the firstsupporting member 21 may include an insulation substrate which has lightpermeability. The insulation substrate may include a glass substrate ora resin substrate.

In each of the preferred embodiments described above, a description hasbeen made about the step of separating the semiconductor wafer source 1by using the laser light irradiation method (Step S5 and Step S6 of FIG.2A). However, the cutting method used in the separating step is notrestricted to the laser light irradiation method, as long as it is ableto efficiently consume the semiconductor wafer source 1.

In place of, or in addition to the laser light irradiation method, thestep of separating the semiconductor wafer source 1 may include at leastany one of a wire saw processing method, a dicing blade processingmethod and an etching processing method. It is preferable that, of thesemethods, the step of separating the semiconductor wafer source 1includes the laser light irradiation method.

In each of the preferred embodiments described above, after removal ofthe element non-formation wafer 42 from the first supporting member 21,the new semiconductor element 52 may be formed at the elementnon-formation wafer 42.

In this case, in order to perform Step S4 to Step S8, the elementnon-formation wafer 42 at which the new semiconductor element 52 isformed may be bonded again to the first supporting member 21. In orderto perform Step S4 to Step S8, the element non-formation wafer 42 atwhich the new semiconductor element 52 is formed may be bonded again toa supporting member different from the first supporting member 21.

In each of the preferred embodiments described above, after removal ofthe second element non-formation wafer 62 from the first supportingmember 21, a new semiconductor element may be formed at the secondelement non-formation wafer 62.

In this case, in order to perform Step S4 to Step S8, the second elementnon-formation wafer 62 at which the new semiconductor element is formedmay be bonded again to the first supporting member 21. In order toperform Step S4 to Step S8, the second element non-formation wafer 62 atwhich the new semiconductor element is formed may be bonded again to asupporting member different from the first supporting member 21.

In each of the preferred embodiments described above, the elementnon-formation wafer 42 may be used in an application other thanformation of the new semiconductor element 52. The element non-formationwafer 42 may be reused as a supporting member for supporting anothersemiconductor wafer source. Another semiconductor wafer source may be asemiconductor wafer source smaller in diameter and thinner in thicknessthan the element non-formation wafer 42.

In each of the preferred embodiments described above, an example ofmanufacturing a vertical type semiconductor device which includes thefirst main surface electrode 30 and the second main surface electrode 45has been shown. However, a horizontal type semiconductor device whichincludes only the first main surface electrode 30 may be manufactured.In this case, the step of forming the second main surface electrode 45is omitted.

In each of the preferred embodiments described above, the step offorming the epitaxial layer 29 may be omitted. That is, a semiconductordevice which is free of the epitaxial layer 29 may be manufactured.

This description shall not restrict any mode of combination of thefeatures shown in the first to the sixth preferred embodiments. Thefirst to the sixth preferred embodiments can be combined in any givenform or in any given mode among these embodiments. That is, a mode thatthe features shown in the first to the sixth preferred embodiments arecombined in any given form or in any given mode is included in examplesof the present invention.

The present application corresponds to Japanese Patent Application No.2017-119704 filed on Jun. 19, 2017 in the Japan Patent Office, and theentire disclose of this application is incorporated herein by reference.

While preferred embodiments of the present invention have been describedin detail, these are merely specific examples used to clarify thetechnical contents of the present invention and the present inventionshould not be interpreted as being limited to these specific examplesand the scope of the present invention is to be limited only by theappended claims.

REFERENCE SIGNS LIST

-   1 Semiconductor wafer source-   2 First main surface of semiconductor wafer source-   3 Second main surface of semiconductor wafer source-   4 Side wall of semiconductor wafer source-   4 First wafer edge portion of semiconductor wafer source-   6 Second wafer edge portion of semiconductor wafer source-   10 Element forming region-   11 Semiconductor element-   21 First supporting member-   22 First supporting main surface of first supporting member-   23 Second supporting main surface of first supporting member-   24 Supporting side wall of first supporting member-   25 First supporting edge portion of first supporting member-   26 Second supporting edge portion of first supporting member-   34 First altered layer-   41 Element formation wafer-   42 Element non-formation wafer-   51 New semiconductor wafer source-   52 New semiconductor element-   55 Second altered layer-   61 Second element formation wafer-   62 Second element non-formation wafer

The invention claimed is:
 1. A method for manufacturing a semiconductor device comprising: a step of preparing a semiconductor wafer source which includes a first main surface on one side, a second main surface on the other side and a side wall connecting the first main surface and the second main surface; an element forming step of setting a plurality of element forming regions on the first main surface of the semiconductor wafer source, and forming a semiconductor element at each of the plurality of element forming regions; a wafer source separating step of cutting the semiconductor wafer source from a thickness direction intermediate portion along a horizontal direction parallel to the first main surface, and separating the semiconductor wafer source into an element formation wafer and an element non-formation wafer after the element forming step; a step of preparing a first supporting member prior to the wafer source separating step, the first supporting member including SiC (silicon carbide); and an attachment step of attaching the first supporting member to the second main surface side of the semiconductor wafer source prior to the wafer source separating step, wherein the wafer source separating step is performed in a state in which the semiconductor wafer source is supported by the first supporting member.
 2. The method for manufacturing the semiconductor device according to claim 1, further comprising: a wafer source reuse step of reusing the element non-formation wafer as a new semiconductor wafer source after the wafer source separating step, and forming a new semiconductor element on a cut surface of the new semiconductor wafer source.
 3. The method for manufacturing the semiconductor device according to claim 2, further comprising: a polishing step of polishing the cut surface of the new semiconductor wafer source after the wafer source separating step and prior to the step of forming the new semiconductor element; wherein the new semiconductor element is formed in the cut surface of the new semiconductor wafer source after the polishing step.
 4. The method for manufacturing the semiconductor device according to claim 2, further comprising: a second wafer source separation step of cutting the new semiconductor wafer source from a thickness direction intermediate portion along a horizontal direction parallel to the cut surface of the new semiconductor wafer source, and separating the new semiconductor wafer source into a second element formation wafer and a second element non-formation wafer after the wafer source reuse step.
 5. The method for manufacturing the semiconductor device according to claim 4, further comprising: a wafer source reuse repeating step of sequentially repeating the wafer source reuse step and the second wafer source separation step.
 6. The method for manufacturing the semiconductor device according to claim 1, wherein the attachment step of the first supporting member is performed prior to the element forming step, and the element forming step is performed in a state in which the semiconductor wafer source is supported by the first supporting member.
 7. The method for manufacturing the semiconductor device according to claim 1, wherein the attachment step of the first supporting member is performed after the element forming step.
 8. The method for manufacturing the semiconductor device according to claim 1, further comprising: a step of preparing a second supporting member prior to the wafer source separating step; and a step of attaching the second supporting member to the first main surface side of the semiconductor wafer source prior to the wafer source separating step; wherein the wafer source separating step is performed in a state in which the semiconductor wafer source is supported by the first supporting member and the second supporting member.
 9. The method for manufacturing the semiconductor device according to claim 1, wherein the wafer source separating step includes an altered layer forming step of forming an altered layer with a crystalline state having altered properties different from properties of other regions, along the horizontal direction in the thickness direction intermediate portion of the semiconductor wafer source, by a laser light being irradiated onto the semiconductor wafer source via the first supporting member, and a step of cutting the semiconductor wafer source along the horizontal direction with the altered layer as a starting point and separating the semiconductor wafer source into the element formation wafer and the element non-formation wafer.
 10. The method for manufacturing the semiconductor device according to claim 9, wherein the altered layer forming step includes a step of irradiating laser light to the thickness direction intermediate portion of the semiconductor wafer source from the second main surface side of the semiconductor wafer source.
 11. The method for manufacturing the semiconductor device according to claim 1, wherein the first supporting member has light permeability; and wherein the wafer source separating step includes an altered layer forming step of forming an altered layer with a crystalline state having altered properties different from properties of other regions, along the horizontal direction in the thickness direction intermediate portion of the semiconductor wafer source, by irradiating laser from the second main surface side of the semiconductor wafer source via the first supporting member, and a step of cutting the semiconductor wafer source along the horizontal direction with the altered layer as a starting point in a state in which the semiconductor wafer source is supported by the first supporting member, and separating the semiconductor wafer source into the element formation wafer and the element non-formation wafer.
 12. The method for manufacturing the semiconductor device according to claim 1, wherein the semiconductor wafer source is made of silicon or silicon carbide.
 13. A wafer-attached structure comprising: a semiconductor wafer source having a first main surface as an element forming surface and a second main surface positioned on the opposite side of the first main surface, and having a thickness sufficient to be cut along a horizontal direction parallel to the first main surface from a thickness direction intermediate portion; a supporting member having a first supporting main surface attached to the second main surface of the semiconductor wafer source and a second supporting main surface positioned on the opposite side of the first supporting main surface; and a bonding layer which is formed at a boundary region between the semiconductor wafer source and the supporting member to bond the semiconductor wafer source and the supporting member, the bonding layer being optically transparent, wherein the semiconductor wafer source includes a first mark indicating a crystal orientation, and the supporting member includes a second mark indicating the crystal orientation of the semiconductor wafer source.
 14. A wafer-attached structure comprising: a semiconductor wafer source having a first main surface as an element forming surface and a second main surface positioned on the opposite side of the first main surface, and having a thickness sufficient to be cut along a horizontal direction parallel to the first main surface from a thickness direction intermediate portion; a supporting member having a first supporting main surface attached to the second main surface of the semiconductor wafer source and a second supporting main surface positioned on the opposite side of the first supporting main surface; and a bonding layer which is formed at a boundary region between the semiconductor wafer source and the supporting member to bond the semiconductor wafer source and the supporting member, the bonding layer being optically transparent, wherein the supporting member includes a supporting side wall connecting the first supporting main surface and the second supporting main surface, a first supporting edge portion which connects the first supporting main surface and the supporting side wall and which is chamfered, and a second supporting edge portion which connects the second supporting main surface and the supporting side wall and which is chamfered. 